-est

(colloquial) verb suffix for the second-person singular preterite


-er

(literary) verb suffix for the impersonal present subjunctive

(literary) verb suffix for the impersonal imperative


-er

brig (“branches, sprigs, shoots”) + -er → briger (“stamens”)

tafl (“sling, catapult”) + -er → tafler (“sling, catapult”)

col (“awn”) + -er → colier (“awner, chobber”)


-ed

From Proto-Brythonic *-hed, from Proto-Celtic *-isetos.

gwan (“weak”) + -ed → gwanned (“as weak”)

rhad (“cheap”) + -ed → rhated (“as cheap”)

cynt (“faster, earlier, sooner”) + -ed → cynted (“as fast, as early, as soon”)

Forms an equative of an adjective of one or two syllables.


-ed

Reduced form of -fed. Cognate with Cornish -es.

pump (“five”) + -ed → pumed (“fifth”)

chwech (“six”) + -ed → chweched (“sixth”)

Used to form the ordinal forms of five and six.


-ed

Ultimately from Proto-Indo-European *-tis or Proto-Indo-European *-tus.

cerdd- (“to walk”, stem) + -ed → cerdded (“to walk”, verbal noun)

clyw- (“to hear”, stem) + -ed → clywed (“to hear”, verbal noun)


-ed

colli (“to lose”) + -ed → colled (“loss”)

sych (“dry”) + -ed → syched (“thirst”)

cymuno (“to take communion, to communicate”) + -ed → cymuned (“community”)


-ed

pryf (“bug, insect”) + -ed → pryfed (“bugs, insects”)

merch (“girl”) + -ed → merched (“girls”)


-ed

(literary) verb suffix for the third-person singular imperative


-io

Variant of -o, initially after a stem that contained /j/ (for Brythonic /ɣ/ or from palatalization after a diphthong), later extended to other verbstems.

Forms verbnouns from verbs and other parts of speech.

-o

Forms verbnouns from verb stems ending in i̯


-or

telyn (“harp”) + -or → telynor (“(male) harpist”)

llên (“literature”) + -or → llenor (“literary man, man o letters”)

carchar (“prison”) + -or → carcharor (“prisoner”)


-id

cadarn (“strong, robust, sturdy”) + -id → cadernid (“strength, robustness, sturdiness”)

rhydd (“free”) + -id → rhyddid (“freedom”)


-id

(literary) verb suffix for the impersonal imperfect/conditional


-ni

glas (“blue, green”) + -ni → glesni (“blueness, chlorosis”)

llwyd (“grey”) + -ni → llwydni (“greyness, mould”)

moel (“bald”) + -ni → moelni (“baldness”)

rhwd (“rust”) + -ni → rhydni (“rustiness, rubigo”)


-u

From Middle Welsh -u, from Proto-Brythonic *-oβ̃.


-ar

From Proto-Brythonic *-ar, from Proto-Celtic *-aros, from Proto-Indo-European *-Hrós. (See byddar (“deaf”).)

cynt (“before, earlier”) + -ar → cynnar (“early”)

diwedd (“end”) + -ar → diweddar (“late”)


-an

bwyell (“axe”) + -an → bwyellan (“small axe, hatchet”)

gwraig (“woman, wife”) + -an → gwreigan (“little woman, little wife”)

barf (“beard”) + -an → barfan (“little beard, goatee, whiskers”)

mud (“mute”) + -an → mudan (“mute person”)

llai (“grey”) + -an → lleian (“nun”)

crwm (“crooked, curved”) + -an → cryman (“sickle, pruning hook”)

person or object with characteristics of the root word

Gwen + -an → Gwennan

Dai + -an → Deian

Elisabeth + -an → Bethan


-an

(colloquial) verb suffix for the third-person future plural


-a

Forms verbnouns from verb stems. Usually denotes an action that is often repeated, e.g. frequenting a certain place or gathering a certain item.


-a

(literary) verb suffix for the third-person singular present indicative/future


-a

(literary) verb suffix for the second-person singular present imperative

(colloquial) verb suffix for the second-person singular present imperative


-a

(colloquial) used to form the superlative of an adjective of one or two syllables.


-a

(colloquial) verb suffix for the first-person singular future


-in

From Proto-Brythonic *-in, from Proto-Celtic *-īnos, from Proto-Indo-European *-iHnos.

hesb (“barren, sterile”) + -in → hesbin (“young ewe”)

crib (“comb”) + -in → cribin (“rake”)

pridd (“soil, earth”) + -in → priddin (“earthen”)

aur (“gold”) + -in → eurin (“golden”)

lledr (“leather”) + -in → lledrin (“leathern”)

(obsolete) forms adjectives from nouns, usually nouns of material

garw (“rough”) + -in → gerwin (“severe, harsh”)


-on

meddyg (“doctor”) + -on → meddygon (“doctors”)

lleidr (“thief”) + -on → lladron (“lladron”)

athro (“(male) teacher”) + -on → athrawon (“athrawon”)


-on

(colloquial) verb suffix for the first-person plural preterite

(colloquial) verb suffix for the third-person plural preterite


-on

aur (“gold”) + -on → euron (“laburnum”)

gŵr (“man”) + -on → gwron (“hero”)

hin (“weather”) + -on → hinon (“fair weather”)


-s

bàth (“bath”) + -s → baths (“baths”)

tomato (“tomato”) + -s → tomatos (“tomatoes”)

gwdihŵ (“owl”) + -s → gwdihŵs (“owls”)


-en

From Middle Welsh -en, from Old Welsh -en, from Proto-Brythonic *-enn. Cognate with Cornish -en, Breton -enn.

llygod (“mice”) + -en → llygoden (“mouse”)

sêr (“stars”) + -en → seren (“star”)

coed (“trees, wood”) + -en → coeden (“tree”)

Used to form the singulative of certain words.

llysywen (“eel”)

matsien (“match”)

taten (“potato”)

pêl (“ball”) + -en → pelen (“little ball, pellet”)

lloer (“moon”) + -en → lloeren (“satellite”)

gwraig (“woman, wife”) + -en → gwreigen (“little woman, little wife”)

coch (“red”) + -en → cochen (“(female) redhead”)

clebr (“gossip, chatter”) + -en → clebren (“(female) gossip”)

gwlith (“dew”) + -en → gwlithen (“slug”)

cwyr (“wax”) + -en → cwyren (“cake or tablet of wax”)

calch (“lime, chalk”) + -en → calchen (“limestone”)

awyr (“sky”) + -en → awyren (“aeroplane”)

crwm (“curved”) + -en → cromen (“dome”)

suffix indicating an object, item, thing


-en

ych (“ox”) + -en → ychen (“oxen”)


-en

(colloquial) verb suffix for the first-person plural conditional

(colloquial) verb suffix for the third-person plural conditional


-o

Dai + -o → Deio

Gwen + -o → Gwenno

Iorwerth + -o → Iolo


-o

(literary) verb suffix for the third-person singular present subjunctive


-o

From Middle Welsh -aw, from Proto-Brythonic *-ọβ̃.

-io

Forms verbnouns from verbs and other parts of speech


-os

plant (“children”) + -os → plantos (“kiddies”)

merched (“girls”) + -os → merchetos (“little girls”)

tai (“houses”) + -os → teios (“small houses”)

diminutive suffix, usually indicating an element of endearment

bedw (“birch”) + -os → bedwos (“birch grove, place where birch grow”)

grug (“heather”) + -os → grugos (“heath”)

brwyn (“rushes”) + -os → brwynos (“brwynos”)

area characterised by a particular plant


-as

teyrn (“monarch, king”) + -as → teyrnas (“kingdom”)

bardd (“poet”) + -as → barddas (“poetry”)

urdd (“order, guild”) + -as → urddas (“honour, dignity”)


-as

(South Wales) (colloquial) verb suffix for the third-person singular preterite


-us

From Middle Welsh -us, from Proto-Brythonic *-ʉs, from Latin -ōsus. Cognate with Cornish -us, Breton -us and English -ous.

blas (“taste”) + -us → blasus (“tasty”)

gwybod (“to know”) + -us → gwybodus (“knowledgeable”)

anffawd (“misfortune”) + -us → anffodus (“unfortunate”)

adjectival suffix often indicating a characteristic, propensity or abundance

chemical nomenclature
chemical nomenclature#English

chemical compound
chemical compound#English

chemical element
chemical element#English

oxidation number
oxidation number#English

(chemistry) -ous, Used in chemical nomenclature to name chemical compounds in which a specified chemical element has a lower oxidation number than in the equivalent compound whose name ends in the suffix -ig. For example asid nitrus (“nitrous acid, HNO₂”) has fewer oxygen atoms per molecule than asid nitrig (“nitric acid, HNO₃”).


-ad

dechrau (“to start, to begin”) + -ad → dechreuad (“start, beginning”)

teimlo (“to feel”) + -ad → teimlad (“feeling”)

dileu (“to delete, to erase”) + -ad → dilead (“deletion, erasure”)


-ad

From Proto-Brythonic *-ad, from earlier *-atus, a late (British) variant of *-ātus, used to form verbal nouns from Celtic ā-stem verbs.

cadw (“to keep”) + -ad → ceidwad (“keeper”)

galw (“to call”) + -ad → geilwad (“caller”)

suffix indicating an agent noun: -er, -or

Ewrop (“Europe”) + -ad → Ewropead (“European”)

Corea (“Korea”) + -ad → Coread (“Korean”)

Norwy (“Norway”) + -ad → Norwyad (“Norwegian”)

person who comes from somewhere or is classed by something, -ian, -ist


-ad

Borrowed from English -ate, altered in the same manner as basged (“basket”).

(chemistry) -ate, suffix denoting one of a group of related compounds - nitrad (“nitrate”), sylffad (“sulfate”).


-i

From Proto-Brythonic *-i, from Proto-Celtic *-esa, plural ending of neuter s-stems like *tegos (“house”) (whence Welsh tŷ, plural tai < *tegos, plural *tegesa). Cognate with Cornish -i.

plwyf (“parish”) + -i → plwyfi (“parishes”)

maen (“stone”) + -i → meini (“stones”)

toiled (“toilet”) + -i → toiledi (“toilets”)


-i

From Old Welsh -im, from Proto-Brythonic *-iβ̃.


-i

diog (“lazy”) + -i → diogi (“laziness”)

truan (“poor, wretched”) + -i → trueni (“pity, shame”)

tlawd (“poor”) + -i → tlodi (“poverty”)


-i

Wil + -i → Wili

Siân + -i → Siani

mam (“mother, mum”) + -i → mami (“mummy”)


-i

(literary) verb suffix for the second-person singular present indicative/future

(colloquial) verb suffix for the second-person singular future


-ir

(literary) verb suffix for the impersonal present indicative/future


-son

verb suffix for the first-person plural preterite

verb suffix for the third-person plural preterite


-et

(colloquial) verb suffix for the second-person singular conditional


-ion

From Proto-Brythonic *-onos, *-onā. Cognate to Cornish -yon, Breton -ien.

seiciatrydd (“psychiatrist”) + -ion → seiciatryddion (“psychiatrists”)

cymydog (“neighbour”) + -ion → cymdogion (“neighbours”)

mab (“son”) + -ion → meibion (“sons”)


-ion

tir (“land”) + -ion → tirion (“territory, plain, grassland”)


-wch

teg (“fair”) + -wch → tegwch (“fairness”)

tawel (“quiet”) + -wch → tawelwch (“quietness, silence”)

hyfryd (“lovely”) + -wch → hyfrydwch (“loveliness”)


-wch

(literary) verb suffix for the second-person plural present indicative/future

(literary) verb suffix for the second-person plural imperative

(colloquial) verb suffix for the second-person plural future

(colloquial) verb suffix for the second-person plural imperative


-ig

From Proto-Celtic *-ikos. Cognate with Cornish -ik, Breton -ig, Proto-Germanic *-igaz, Ancient Greek -ικός (-ikós), Latin -icus.

afon (“river”) + -ig → afonig (“rivulet”)

barwn (“baron”) + -ig → barwnig (“baronet”)

oen (“lamb”) + -ig → oenig (“small ewe lamb”)

lloer (“moon”) + -ig → lloerig (“lunatic”)

ysgol (“school”) + -ha + -ig → ysgolhaig (“scholar”)

calan (“first day of the year”) + -ig → calennig (“New Year's gift”)

person or object with characteristics of the root word

gwenwyn (“poison”) + -ig → gwenwynig (“poisonous”)

pwys (“weight, pound”) + -ig → pwysig (“important”)

Gwyddel (“Irish man”) + -ig → Gwyddelig (“Irish”)

(chemistry) -ic, Used in chemical nomenclature to name chemical compounds in which a specified chemical element has a higher oxidation number than in the equivalent compound whose name ends in the suffix -us. For example asid nitrig (“nitric acid, HNO₃”) has more oxygen atoms per molecule than asid nitrus (“nitrous acid, HNO₂”).


-ol

From Middle Welsh -awl, from Proto-Brythonic *-ọl, from Proto-Celtic *-ālos, reinforced by Latin -ālis.

arian (“money”) + -ol → ariannol (“financial”)

proffesiwn (“profession”) + -ol → proffesiynol (“professional”)

cychwyn (“to start”) + -ol → cychwynnol (“initial”)

iachus (“healthy”) + -ol → iachusol (“heath-giving, heath-promoting”)


-ol

(organic chemistry) -ol (suffix denoting an alcohol or phenol)


-ant

maddau (“to forgive”) + -ant → maddeuant (“forgiveness”)

show the action of a verb or its result, -tion, -ment


-ant

(literary) verb suffix for the third-person plural present indicative/future


-om

(literary) verb suffix for the first-person plural present subjunctive


-es

From the Proto-Brythonic -issā, ultimately borrowed from (or perhaps cognate to) Latin -issa, whence also English -ess. Cognate with Cornish -es.

athro (“male teacher”) + -es → athrawes (“female teacher”)

gweinydd (“waiter”) + -es → gweinyddes (“waitress”)

Norwy (“Norway”) + -es → Norwyes (“Norwegian woman”)

cadno (“fox”) + -es → cadnawes (“vixen”)


-es

brân (“crow”) + -es → branes (“flight of crows”)

llong (“ship”) + -es → llynges (“navy, fleet”)


-es

(colloquial) verb suffix for the first-person singular preterite


-ent

(literary) verb suffix for the third-person plural imperfect/conditional

(literary) verb suffix for the third-person plural imperative


-ai

enwebu (“to nominate”) + -ai → enwebai (“nominee”)

cyf-weld (“to interview”) + -ai → cyfwelai (“interviewee”)

morgeisio (“to mortgage”) + -ai → morgeisai (“mortgagee”)

blawd (“flour”) + -ai → blotai (“beggar of flour; flour merchant”)

llad (“gift, virtue”) + -ai → llatai (“love messenger, go-between”)

cymell (“to compel, to induce”) + -ai → cymhellai (“wrench”)

hidlo (“to strain, to filter”) + -ai → hidlai (“strainer, filter”)

ul (“moist, damp”) + -ai → ulai (“hydrogen”)

ufel (“fire”) + -ai → ufelai (“oxygen”)


-ai

(literary) verb suffix for the third-person singular imperfect/conditional

(colloquial) verb suffix for the third-person singular conditional


-ach

From Middle Welsh -ach, from Proto-Brythonic *-ox, with the vowel altered by influence from -af.

ifanc (“young”) + -ach → ifancach (“younger”)

pwysig (“important”) + -ach → pwysicach (“more important”)

tlawd (“poor”) + -ach → tlotach (“poorer”)


-ach

cor (“dwarf”) + -ach → corrach (“dwarf, gnome”)

cawl (“soup”) + -ach → cawlach (“mess, hotchpotch”)

dillad (“clothes”) + -ach → dilladach (“old clothes, worthless clothing”)


-ach

cyfrin (“privy, cryptic”) + -ach → cyfrinach (“secret”)

cyfaill (“friend”) + -ach → cyfeillach (“fellowship, companionship”)

clinc (“clink, tinkle”) + tarddu (“emerge, erupt”) + -ach → clindarddarch (“crackling; to crackle”)

suffix forming abstract nouns and some verbnouns


-yn

From Middle Welsh -yn, from Proto-Brythonic *-ɨnn.

winwns (“onions”) + -yn → winwnsyn (“onion”)

plant (“children”) + -yn → plentyn (“child”)

dillad (“clothes”) + -yn → dilledyn (“item of clothing, piece of clothing”)

Used to form the singulative of certain words.

diferu (“to drop, to drip”) + -yn → diferyn (“drop, drip”)

planhigion (“plants”) + -yn → planhigyn (“plant”)

degolion (“decimals”) + -yn → degolyn (“decimal”)

llyfr (“book”) + -yn → llyfryn (“booklet”)

arf (“weapon, tool”) + -yn → erfyn (“tool, instrument”)

clwt (“rag”) + -yn → clwtyn (“(little) rag”)

cardota (“to beg”) + -yn → cardotyn (“beggar”)

meddw (“drunk”) + -yn → meddwyn (“drunkard”)

crwydro (“to wander”) + -yn → crwydryn (“vagrant”)

gwydr (“glass”) + -yn → gwydryn (“(drinking) glass”)

newid (“change”) + -yn → newidyn (“variable”)

misol (“monthly”) + -yn → misolyn (“monthly (periodical)”)

echdynnu (“to extract”) + -yn → echdynnyn (“extract”)

suffix indicating an object, item, thing


-it

(literary) verb suffix for the second-person singular imperfect/conditional


-ys

nyrs (“nurse”) + -ys → nyrsys (“nurses”)

bocs (“box”) + -ys → bocsys (“boxes”)

bỳs (“bus”) + -ys → bysys (“buses”)


-ys

gwybod (“know”) + -ys → gwyddys (“is known, one knows”)

verb suffix for the impersonal present indicative/future


-au

From Middle Welsh -eu, from Old Welsh -ou, from Proto-Brythonic *-ow, from Proto-Celtic *-owes, u-stem nominative plural. Cognate with Cornish -ow and Breton -où.

syniad (“idea”) + -au → syniadau (“ideas”)

methiant (“failure”) + -au → methiannau (“failures”)

gwasanaeth (“service”) + -au → gwasanaethau (“services”)


-au

Alternative form of -hau (forms verbal nouns)

-áu

when there is confusion with an identically-spelled plural


-em

(literary) verb suffix for the first-person plural imperfect/conditional


-leg

Adapted from English -logy with influence from native -eg.

bio- (“bio-”) + -leg → bioleg (“biology”)

ffeno- (“pheno-”) + -leg → ffenoleg (“phenology”)


-od

buwch (“cow”) + -od → buchod (“cows”)

cath (“cat”) + -od → cathod (“cats”)

eliffant (“elephant”) + -od → eliffantod (“elephants”)

menyw (“woman”) + -od → menywod (“women”)

Gwyddel (“Irish man”) + -od → Gwyddelod (“Irish people”)


-od

dwrn (“fist”) + -od → dyrnod (“punch, thump”)

cleddyf (“sword”) + -od → cleddyfod (“sword stroke, gash”)

ffon (“stick”) + -od → ffonnod (“stroke with a stick, stripe”)


-od

rhyfedd (“strange, wondrous”) + -od → rhyfeddod (“wonder”)


-sen

(colloquial) verb suffix for the first-person plural conditional

(colloquial) verb suffix for the third-person plural conditional


-adur

From Proto-Brythonic *-adʉr. Cf. Latin -ātor.

ffoi (“to flee”) + -adur → ffoadur (“refugee”)

hen (“old”) + -adur → henadur (“elder, presbyter”)

agent suffix; usually added to a verbal root

enwi (“to name”) + -adur → enwadur (“glossary”)

merthyr (“martyr”) + -adur → merthyradur (“martyrology”)

mwy (“bigger”) + -adur → mwyadur (“microscope”)

palu (“to dig”) + -adur → pladur (“scythe”)


-aid

cwpan (“cup”) + -aid → cwpanaid (“cupful”)

llwy (“spoon”) + -aid → llwyaid (“spoonful”)

potel (“bottle”) + -aid → potelaid (“bottleful”)

Forming nouns denoting the amount contained, -ful


-aid

meudwy (“hermit”) + -aid → meudwyaid (“hermits”)

Pharo (“Pharaoh”) + -aid → Pharoaid (“Pharaohs”)


-red

Ultimately from Proto-Indo-European *Hret-, whence also rhedeg (“to run”). Cognate with Old Irish -rad.

gwaith (“work”) + -red → gweithred (“action”)

lled (“width”) + -red → lledred (“latitude”)

cylch (“circle”) + -red → cylchred (“cycle”)


-og

From Middle Welsh -awc, from Proto-Brythonic *-ọg, from Proto-Celtic *-ākos, from Proto-Indo-European *-eh₂kos, *-eh₂ḱos, from a-stem suffix *-eh₂ + adjectival suffix *-kos, *-ḱos. Akin to Cornish -ek, Breton -eg, Irish -ach, Scottish Gaelic -ach, Manx -agh, Latin -ācus, -īcus and English -y.

carreg (“stone”) + -og → caregog (“stony”)

twll (“hole”) + -og → tyllog (“porous”)

gallu (“ability”) + -og → galluog (“capable”)

enw (“name”) + -og → enwog (“famous”)

adjectival suffix often indicating an abundance of the root

perchen (“to own”) + -og → perchennog (“owner”)

march (“stallion, horse”) + -og → marchog (“knight, horserider”)

draen (“thorn(s)”) + -og → draenog (“hedgehog”)

ysgyfarn (“ear”) + -og → ysgyfarnog (“hare”)

clust (“ear”) + -og → clustog (“cushion, bolster”)

noun suffix indicating person, creature or object characterised by root


-eg

Llydaw (“Brittany”) + -eg → Llydaweg (“Breton language”)

Gwyddel (“Irishman”) + -eg → Gwyddeleg (“Irish language”)

Indonesia (“Indonesia”) + -eg → Indoneseg (“Indonesian language”)

peiriant (“machine, engine”) + -eg → peirianneg (“engineering”)

rheswm (“reason”) + -eg → rhesymeg (“logic”)

electron (“electron”) + -eg → electroneg (“electronics”)


-iau

cadair (“chair”) + -iau → cadeiriau (“chairs”)

dydd (“day”) + -iau → dyddiau (“days”)

clwb (“club”) + -iau → clybiau (“clubs”)


-ter

From Proto-Celtic *-teros (comparative suffix), from Proto-Indo-European *-teros. Cognate with Cornish -ter.

inh

craff (“observant, astute”) + -ter → craffter (“astuteness”)

gwag (“empty”) + -ter → gwacter (“emptiness”)

pell (“far”) + -ter → pellter (“distance”)


-ell

From Proto-Brythonic *-ell, in at least some cases from Latin -illa. Cognate with Cornish -ell.

rhathu (“rub, scrape”) + -ell → rhathell (“file, rasp”)

bys (“finger”) + -ell → bysell (“(computer keyboard) key”)

allwedd (“(house, piano) key”) + -ell → allweddell (“keyboard”)

traeth (“beach”) + -ell → traethell (“strand, sandbank”)

pib (“pipe”) + -ell → pibell (“pipe”)

iwrch (“roe deer”) + -ell → iyrchell (“female or young roe deer”)


-iaeth

From Proto-Brythonic *-aɨθ, from Insular Celtic *-axtā, suffixal use of Proto-Celtic *axtā. Cognate with Cornish -ieth.

arwr (“hero”) + -iaeth → arwriaeth (“heroism”)

deintydd (“dentist”) + -iaeth → deintyddiaeth (“dentistry”)

cydnabod (“recognise, acknowledge”) + -iaeth → cydnabyddiaeth (“recognition, acknowledgement”)

llaw (“hand”) + trin (“to treat”) + -iaeth → llawdriniaeth (“surgery”)

barwn (“baron”) + -iaeth → barwniaeth (“baronage, barony”)

territory controlled by, -ship, -age, -y, -dom


-der

From Proto-Celtic *-teros (comparative suffix), from Proto-Indo-European *-teros. Cognate with Cornish -der.

dewr (“brave”) + -der → dewrder (“bravery”)

prin (“rare, scarce”) + -der → prinder (“lack, scarcity”)

eang (“wide”) + -der → ehangder (“breadth, expanse”)


-w

Megan + -w → Begw

Ann + -w → Nanw

Siân + -w → Sianw


-af

From Proto-Brythonic *-haβ̃, from Proto-Celtic *-isamos. Cognate with Cornish -a.

Used to form the superlative of an adjective of one or two syllables.


-af

(literary) verb suffix for the first-person singular present indicative/future

(colloquial) verb suffix for the first-person singular future


-oedd

According to Pedersen and Jackson, from both Proto-Celtic *-eyes (the nominative plural of masculine and feminine i-stems, from Proto-Indo-European *-eyes) and Proto-Celtic *-esa (the nominative/accusative plural of neuter s-stems, from Proto-Indo-European *-esh₂); for the development in the latter case compare oedd (“was”) from *esāt (Latin erat).
According to Morris Jones, from both Proto-Celtic *-iyes (the same ending as Pedersen’s *-eyes) and *-iyoi (the nominative plural of masculine yo-stems) when the stress fell on the antepenult.
According to Schrijver, from a Proto-Celtic *-es-ī that arose when certain neuter s-stems became masculine; Schrijver holds -ydd as the sole descendant of *-eyes.

llyfrgell (“library”) + -oedd → llyfrgelloedd (“libraries”)

cwm (“valley”) + -oedd → cymoedd (“valleys”)

cant (“hundred”) + -oedd → cannoedd (“hundreds”)


-fed

From Proto-Brythonic *-β̃ed, from Proto-Celtic *-metos. Cognate with Cornish -ves. Compare Old Irish -mad and Modern Irish -ú (formerly spelled -mhadh).

-th (suffix forming the ordinal form of numerals)


-wr

From gŵr (“man”), but semantically influenced due to similarity in form to English -er and Latin -or.

tafarn (“pub”) + -wr → tafarnwr (“landlord”)

trydan (“electricity”) + -wr → trydanwr (“electrician”)

Sbaen (“Spain”) + -wr → Sbaenwr (“Spaniard”)

darlledu (“broadcast”) + -wr → darlledwr (“broadcaster”)

suffix indicating a person, especially an agent noun: -er, -or

copïo (“to copy”) + -wr → copïwr (“copier”)

sychu (“to dry”) + -wr → sychwr (“drier”)

suffix indicating an instrument or machine: -er, -or


-ydd

cyfarfod (“meeting”) + -ydd → cyfarfodydd (“meetings”)

afon (“river”) + -ydd → afonydd (“rivers”)

gwaun (“moor, heath”) + -ydd → gweunydd (“moors, heaths”)


-ydd

From Proto-Brythonic *-ɨð, from Proto-Celtic *‑iyū. Cognate with Cornish -ydh.

cig (“meat”) + -ydd → cigydd (“butcher”)

adar (“birds”) + -ydd → adarydd (“ornithologist”)

llywio (“to steer”) + -ydd → llywydd (“president”)

suffix indicating a person, especially an agent noun: -er, -or, -ist

hydoddi (“to dissolve”) + -ydd → hydoddydd (“solvent”)

adweithio (“to react”) + -ydd → adweithydd (“reactor”)

taflunio (“to project”) + -ydd → taflunydd (“projector”)

suffix indicating an instrument, machine or substance, especially an agent noun: -er, -or


-ydd

llafar (“spoken, oral”) + -ydd → lleferydd (“speech”)

llawn (“full”) + -ydd → llonydd (“still, quiet”)


-aidd

From Middle Welsh -eid, from Proto-Celtic *‑adi̯os. Cognate with Old Irish -de, Greek -άδα (-áda), Latin -idus.

eliffant (“elephant”) + -aidd → eliffantaidd (“elephantine”)

coch (“red”) + -aidd → cochaidd (“reddish”)

Cymreig (“Welsh”) + -aidd → Cymreigaidd (“Welshy”)

Rwsia (“Russia”) + -aidd → Rwsaidd (“Russian”)


-aeth

From Proto-Brythonic *-aɨθ, from Insular Celtic *-axtā, suffixal use of Proto-Celtic *axtā. Cognate with Cornish -eth, Breton -ezh, Irish -acht, Scottish Gaelic -achd and Manx -aght.

aelod (“member”) + -aeth → aelodaeth (“membership”)

cyflog (“wage”) + -aeth → cyflogaeth (“employment”)

meddyg (“doctor”) + -aeth → meddygaeth (“medicine”)

amau (“to doubt”) + -aeth → amheuaeth (“doubt”)

ymherodr (“emperor”) + -aeth → ymerodraeth (“empire”)

esgob (“bishop”) + -aeth → esgobaeth (“diocese, bishopric”)


-iad

caru (“to love”) + -iad → cariad (“love”)

penodi (“to appoint”) + -iad → penodiad (“appointment”)

cyfieithu (“to translate”) + -iad → cyfieithiad (“translation”)

shows the action of a verb or its result


-iad

From Proto-Brythonic *-ad, from earlier *-atus, a late (British) variant of *-ātus, used to form verbal nouns from Celtic ā-stem verbs. The -i- is secondary. Cognate with Cornish -yas.

dal (“to hold”) + -iad → deiliad (“holder”)

lladd (“to kill”) + -iad → lleiddiad (“assassin; killer whale”)

suffix indicating an agent noun: -er, -or

Israel (“Israel”) + -iad → Israeliad (“Israeli; Israelite”)

Rhufain (“Rome”) + -iad → Rhufeiniad (“Roman”)

amldduw (“polytheistic”) + -iad → amldduwiad (“polytheist”)

person who comes from somewhere or is classed by something, -ian, -ist


-edig

From Proto-Brythonic *-ẹdig, from Proto-Celtic *-atīkos, probably from a combination of Proto-Indo-European *-eh₂t- + *-kos.
Cognate with Cornish -esik and more distantly Latin -āticus.

amgáu (“to enclose”) + -edig → amgaeedig (“enclosed”)

cysegru (“to consecrate”) + -edig → cysegredig (“consecrated”)

ysgrifennu (“to write”) + -edig → ysgrifenedig (“written”)

adjectival suffix forming deverbal adjectives -ed

caru (“to love”) + -edig → caredig (“kind”)

nodi (“to note”) + -edig → nodedig (“noteable, noteworthy”)

troi (“to turn”) + -edig → troëdig (“turning, twisting, perverted”)

adjectival suffix indicating having characteristics the root


-hau

head

-hau (first-person singular present -haf)

Originally causative/denominative; from Proto-Brythonic *-haɣjed, from Proto-Celtic *-sagyetor (causative/denominative suffix). Cognate with Old Irish -igidir (Irish -igh, Manx -ee, Scottish Gaelic -ich).

inh

creates a verbal noun from an adjectival root


-fa

head

-fa f (plural -feydd or -faoedd or -fâu)

-feydd (plural)
-faoedd (plural)
-fâu (plural)

From Proto-Celtic *magos (“field”). Compare Cornish -va, Old Irish mag, from Proto-Indo-European *méǵh₂s.
According to Morris-Jones, in some cases (such as lladdfa) instead from the verbnoun ending -fan (as in hedfan), from Proto-Celtic *-man.

swydd (“job”) + -fa → swyddfa (“office”)

meddyg (“doctor”) + -fa → meddygfa (“doctor's surgery”)

myned (“to go”) + -fa → mynedfa (“entrance”)

amlosgi (“to cremate”) + -fa → amlosgfa (“crematorium”)

Used to derive places from verbs and nouns.

cyboli (“to jumble”) + -fa → cybolfa (“hotchpotch, jumble”)

cosi (“to itch; to beat”) + -fa → cosfa (“itch; beating, hiding”)

dal (“to catch, to seize”) + -fa → dalfa (“custody”)

Used to derive actions and states from verbs and nouns.


-odd

(literary) verb suffix for the third-person singular preterite

(colloquial) verb suffix for the third-person singular preterite


-ech

(literary) verb suffix for the second-person plural imperfect/conditional

(colloquial) verb suffix for the second-person plural conditional


-adwy

credu (“to believe”) + -adwy → credadwy (“believable”)

dibynnu (“to depend”) + -adwy → dibynadwy (“dependable”)

bioddiraddio (“to biodegrade”) + -adwy → bioddiraddiadwy (“biodegradable”)

ofni (“to fear”) + -adwy → ofnadwy (“terrible”)

adjectival suffix indicating capability to be -able, -ible

rhuo (“to roar”) + -adwy → rhuadwy (“roaring”)

sefyll (“to stand”) + -adwy → safadwy (“standing”)

adjectival suffix indicating the performing the root


-och

(literary) verb suffix for the second-person plural present subjunctive

(colloquial) verb suffix for the second-person plural preterite


-iol

From Middle Welsh -awl, from Proto-Brythonic *-ọl, from Proto-Celtic *-ālos, reinforced by Latin -ālis.

budd (“benefit”) + -iol → buddiol (“beneficial”)

dinistr (“destruction”) + -iol → dinistriol (“destructive”)

bygwth (“to threaten”) + -iol → bygythiol (“threatening”)

gwraidd (“root”) + -iol → gwreiddiol (“original”)


-ych

aur (“gold”) + -ych → eurych (“goldsmith”)


-ych

(literary) verb suffix for the second-person singular present subjunctive


-ha

In some cases, ultimately from Proto-Indo-European *seh₂g- (“to seek”).

pysgod (“fish”) + -ha → pysgota (“to fish”)

bwyd (“food”) + -ha → bwyta (“to eat”)


-ith

(colloquial) verb suffix for the third-person singular future


-iant

chwyddo (“to swell, to inflate”) + -iant → chwyddiant (“inflation, distention”)

hydoddi (“to dissolve”) + -iant → hydoddiant (“solution”)

ffynnu (“to prosper, to flourish”) + -iant → ffyniant (“prosperity, success”)

show the action of a verb or its result, -tion, -ment


-deb

absennol (“absent”) + -deb → absenoldeb (“absence”)

prydlon (“punctual, prompt”) + -deb → prydlondeb (“punctuality”)

pur (“pure”) + -deb → purdeb (“purity”)


-tod

esgeulus (“negligent, careless”) + -tod → esgeulustod (“negligence, carelessness”)

mall (“plague, pestilence”) + -tod → malltod (“blight, blast”)

hwylus (“expedient, handy”) + -tod → hwylustod (“expediency”)


-dod

From Middle Welsh -dawt, ultimately from Proto-Indo-European *-teh₂ts. Cognate with Cornish -ses, Latin -tas, Ancient Greek -της (-tēs), and Sanskrit -ताति (-tāti).

un (“one”) + -dod → undod (“unity”)

cybydd (“miser”) + -dod → cybydd-dod (“miserliness”)

baban (“baby”) + -dod → babandod (“infancy”)


-iadur

gair (“word”) + -iadur → geiriadur (“dictionary”)

dydd (“day”) + -iadur → dyddiadur (“diary”)

blwydd (“year”) + -iadur → blwyddiadur (“yearbook, annual”)

cyfrifo (“to count, to compute”) + -iadur → cyfrifiadur (“computer”)

rheoli (“to rule, to regulate”) + -iadur → rheoliadur (“pace maker”)

cengl (“skein, slip of yarn”) + -iadur → cengliadur (“reel, yarnwindle”)

agent suffix; usually added to a verbal root


-wraig

fferm (“farm”) + -wraig → ffermwraig (“female farmer, farmer's wife”)

tafarn (“pub”) + -wraig → tafarnwraig (“landlady”)

myfyrio (“to meditate”) + -wraig → myfyrwraig (“female student”)


-iach

oel (“oil”) + -iach → oeliach (“oils, oil stains”)

gêr (“gear”) + -iach → geriach (“tackle, gear, odds and ends”)


-iff

(South Wales, colloquial) verb suffix for the third-person singular future


-swn

(colloquial) verb suffix for the first-person singular conditional


-asid

(literary) verb suffix for the impersonal pluperfect


-wyd

(literary) verb suffix for the impersonal preterite


-asent

(literary) verb suffix for the third-person plural pluperfect


-asant

(literary) verb suffix for the third-person plural preterite


-asit

(literary) verb suffix for the second-person singular pluperfect


-asom

(literary) verb suffix for the first-person plural preterite


-asech

(literary) verb suffix for the second-person plural pluperfect


-asem

(literary) verb suffix for the first-person plural pluperfect


-aswn

(literary) verb suffix for the first-person singular pluperfect


-asoch

(literary) verb suffix for the second-person plural preterite


-eb

anfon (“to send”) + -eb → anfoneb (“invoice”)

talu (“to pay”) + -eb → taleb (“voucher”)

manwl (“detail”) + -eb → manyleb (“specification”)

cof (“memory”) + -eb → cofeb (“memorial”)

hen (“old”) + -eb → heneb (“ancient monument”)

organ (“organ”) + -eb → organeb (“organism”)

cyllid (“finance”) + -eb → cyllideb (“budget”)

diwedd (“end”) + -eb → diweddeb (“cadence, close”)

disgyn (“to descend”) + -eb → disgynneb (“anticlimax, bathos”)


-ont

(literary) verb suffix for the third-person plural present subjunctive


-asai

(literary) verb suffix for the third-person singular pluperfect


-aist

(literary) verb suffix for the second-person singular preterite

(colloquial) verb suffix for the second-person singular preterite


-wn

(literary) verb suffix for the first-person plural present indicative/future

(literary) verb suffix for the first-person singular imperfect/conditional

(literary) verb suffix for the first-person plural imperative

(colloquial) verb suffix for the first-person plural future

(colloquial) verb suffix for the first-person singular conditional


-set

(colloquial) verb suffix for the second-person singular conditional


-wyf

(literary) verb suffix for the first-person singular present subjunctive


-ws

Dic + -ws → Dicws

Ann + -ws → Nanws

Catrin + -ws → Catws


-ws

Beth wetws 'i?

(South Wales) (colloquial) verb suffix for the third-person singular preterite


-cyn

bryn (“hill”) + -cyn → bryncyn (“hillock”)

lle (“place”) + -cyn → llecyn (“small place, spot”)

Huw (“Huw”) + -cyn → Huwcyn (“little Huw (pet name)”)

celfi (“furniture”) + -cyn → celficyn (“piece of furniture”)

Used to form the singulative of certain words.


-mon

tir (“ground”) + -mon → tirmon (“groundsman”)


-awdwr

From Middle Welsh -awdyr, from Proto-Brythonic *-ọdr, from Latin -ātor, assimilated to the suffix -wr.

creu (“to create”) + -awdwr → creawdwr (“creator”)

iach (“healthy; saved”) + -awdwr → iachawdwr (“saviour”)

suffix indicating a person, especially an agent noun: -er, -or


-ioni

da (“good”) + -ioni → daioni (“goodness”)

drwg (“bad”) + -ioni → drygioni (“mischief”)

hael (“generous”) + -ioni → haelioni (“generosity”)


-yd

iach (“healthy”) + -yd → iechyd (“health”)

claf (“sick, ill”) + -yd → clefyd (“disease”)

mab (“son”) + -yd → mebyd (“childhood, infancy”)


-dwr

glew (“courageous, brave”) + -dwr → glewdwr (“courage, bravery”)

sych (“dry”) + -dwr → sychdwr (“drought”)

cryf (“strong”) + -dwr → cryfdwr (“strength”)


-dra

byr (“short”) + -dra → byrdra (“shortness, brevity”)

glanwaith (“cleanly, hygenic”) + -dra → glanweithdra (“cleanliness, hygiene”)

anwaraidd (“barbaric, uncivilised”) + -dra → anwareidd-dra (“barbarity”)


-rwydd

sicr (“certain”) + -rwydd → sicrwydd (“certainty”)

hapus (“happy”) + -rwydd → hapusrwydd (“happiness”)

amherffaith (“imperfect”) + -rwydd → amherffeithrwydd (“imperfection”)


-ineb

call (“sensible, sane”) + -ineb → callineb (“sense, sanity”)

doeth (“wise”) + -ineb → doethineb (“wisdom”)

ffraeth (“witty”) + -ineb → ffraethineb (“wit, wittiness”)


-llon

dig (“anger, wrath”) + -llon → dicllon (“angry, wrathful”)

adjectival suffix, often indicating a characteristic or fulness -ful


-fel

oer (“cold, chilly”) + -fel → oerfel (“cold, coldness, chill”)


-tid

From Middle Welsh -tit, from Proto-Brythonic *-tid, from Proto-Celtic *-tūss (stem *-tūt-; compare Old Irish -tu), from Proto-Indo-European *-tuHts (whence Latin -tūs and Gothic -𐌳𐌿𐌸𐍃 (-dūþs)).

ieuanc (“young”) + -tid → ieuenctid (“youth”)


-lon

cyfraith (“law”) + -lon → cyfreithlon (“legal”)

ffrwyth (“fruit”) + -lon → ffrwythlon (“fruitful, fertile”)

rhad (“grace”) + -lon → rhadlon (“genial”)

bodd (“consent”) + -lon → bodlon (“willing, satisfied”)


-awd

dau (“two”) + -awd → deuawd (“duo, duet”)

tri (“three”) + -awd → triawd (“trio”)

pump (“five”) + -awd → pumawd (“quintet”)

deg (“ten”) + -awd → degawd (“decade”)

pêl (“ball”) + -awd → pelawd (“over (cricket)”)

agor (“to open”) + -awd → agorawd (“overture”)

pen (“head”) + -awd → pennawd (“headline”)

anian (“nature”) + -awd → anianawd (“temperament”)


-lyd

From lled (“width”) or lled- (“partially”), both probably from the same source word ultimately.

baw (“muck”) + -lyd → bawlyd (“mucky”)

cybydd (“miser”) + -lyd → cybyddlyd (“miserly, covetous”)

llwch (“dust”) + -lyd → llychlyd (“dusty”)

drysu (“to confuse”) + -lyd → dryslyd (“confused”)

sbeis (“spice”) + -lyd → sbeislyd (“spicy, hot”)

pejorative adjectival suffix, often indicating tendency to or abundance of


-llyd

saim (“grease, fat”) + -llyd → seimllyd (“greasy”)

rhew (“ice, frost”) + -llyd → rhewllyd (“icy, frosty”)

rhagfarn (“prejudice”) + -llyd → rhagfarnllyd (“prejudiced”)

chwerthin (“to laugh”) + -llyd → chwerthinllyd (“laughable, risible”)


-did

From Middle Welsh -dit, from Proto-Celtic *-tūss, from Proto-Indo-European *-tuHts. Cognate with Latin -tus and Proto-Germanic *-dūþiz.

glân (“clean”) + -did → glendid (“cleanliness”)

gwan (“weak”) + -did → gwendid (“weakness”)

calon (“heart”) + -did → calondid (“encouragement”)


-gar

From Proto-Celtic *-āk-aro-, equivalent to -og + -ar. The sense of liking or fondness is influenced by caru (“to love”).

meddwl (“thought”) + -gar → meddylgar (“thoughtful, considerate”)

traidd (“penetration”) + -gar → treiddgar (“penetrating”)

lliw (“colour”) + -gar → lliwgar (“colourful”)

adjectival suffix, often indicating tendency, -ful

arian (“money”) + -gar → ariangar (“money-loving, covetous”)

gwlad (“country”) + -gar → gwlatgar (“patriotic”)

darllen (“to read”) + -gar → darllengar (“fond of reading”)

adjectival suffix indicating a like or fondness of, -loving


-tra

erchyll (“hideous, horrible”) + -tra → erchylltra (“hideousness, horror”)

galanas (“blood-feud, enmity”) + -tra → galanastra (“slaughter, massacre”)

gorffwyll (“mad, insane”) + -tra → gorffwylltra (“madness, insanity”)


-edd

From Middle Welsh -eð, from Proto-Brythonic *-eð (whence also Cornish -edh), from Proto-Celtic *-iyā (whence also Old Irish -e), from Proto-Indo-European *-i-eh₂. Cognate with Ancient Greek -ίᾱ (-íā) and Latin -ia.

anabl (“unable, disabled”) + -edd → anabledd (“disability”)

mawr (“big, great”) + -edd → mawredd (“greatness”)

cymesur (“symmetrical”) + -edd → cymesuredd (“symmetry”)

amgylch (“surroundings”) + -edd → amgylchedd (“environment”)


-edd

From Proto-Celtic *-iyās, nominative plural of *ī-stem feminine nouns like *rīganī (“queen”) (whence Welsh rhiain (“maiden”), plural rhianedd), from Proto-Indo-European *-ih₂es, nominative plural to nouns in *-ih₂.

gwraig (“woman, wife”) + -edd → gwragedd (“women, wives”)

rhiain (“maiden”) + -edd → rhianedd (“maidens”)

teyrn (“monarch, kind”) + -edd → teyrnedd (“monarchs, kings”)


-aint

hen (“old”) + -aint → henaint (“old age”)

dioddef (“suffer”) + -aint → dioddefaint (“suffering, passion”)


-aint

gof (“blacksmith”) + -aint → gofaint (“blacksmiths”)

câr (“relative”) + -aint → ceraint (“relatives”)

nai (“nephew”) + -aint → neiaint (“nephews”)


-iaid

anifail (“animal”) + -iaid → anifeiliaid (“animals”)

pechadur (“sinner”) + -iaid → pechaduriaid (“sinners”)

Morgan (“Morgan”) + -iaid → Morganiaid (“Morgans”)


-iadau

awgrym (“suggestion”) + -iadau → awgrymiadau (“suggestions”)

protest (“protest”) + -iadau → protestiadau (“protests”)

apêl (“appeal”) + -iadau → apeliadau (“appeals”)


-yr

brawd (“brother”) + -yr → brodyr (“brothers”)


-iog

adain (“wing”) + -iog → adeiniog (“winged”)

baich (“club”) + -iog → beichiog (“burdened; pregnant”)

cwrl (“curl”) + -iog → cyrliog (“curly”)

gair (“word”) + -iog → geiriog (“wordy”)

adjectival suffix often indicating an abundance of the root


-eiddio

rhew (“ice”) + -eiddio → rheweiddio (“to refrigerate; refrigeration”)

English animate + -eiddio → animeddio (“to animate; animation”)


-edydd

gwylio (“to watch”) + -edydd → gwyliedydd (“watchman, senitel”)

asio (“to join”) + -edydd → asiedydd (“joiner”)

dringo (“to climb”) + -edydd → dringhedydd (“climber”)

suffix indicating a person, or rarely an animal or plant, especially an agent noun: -er, -or, -ist

chwilio (“to search”) + -edydd → chwiliedydd (“probe”)

suffix indicating an instrument, machine or substance, especially an agent noun: -er, -or


-iedydd

taflu (“to throw”) + -iedydd → tafliedydd (“thrower”)

dwyn (“to bear”) + -iedydd → dygiedydd (“bearer”)

gyrru (“to drive”) + -iedydd → gyriedydd (“driver, drover”)

anadlu (“to breathe”) + -iedydd → anadliedydd (“breathalyser”)


-iwr

From gŵr (“man”), but semantically influenced due to similarity in form to English -er and Latin -or.

pêl-droed (“football, soccer”) + -iwr → pêl-droediwr (“footballer, soccer player”)

cyfraith (“law”) + -iwr → cyfreithiwr (“solictor, lawyer, attorney”)

Rhufain (“Rome”) + -iwr → Rhufeiniwr (“Roman”)


-pwyd

(literary) verb suffix for the impersonal preterite


-fedd

Related to medd (“authority, rule”) and meddu (“to possess”); ultimately from Proto-Indo-European *med- (“to measure; give advice”).

der

mawd (“thumb”) + -fedd → modfedd (“inch”)

ewin (“fingernail”) + -fedd → ewinfedd (“fingernail's breadth; a tiny amount”)

ton (“wave”) + -fedd → tonfedd (“wavelength”)

forming nouns denoting lengths or units of length, -length


-anaeth

drud (“expensive”) + -anaeth → drudanaeth (“costliness”)


-aniaeth

gwlyb (“wet”) + -aniaeth → gwlybaniaeth (“moisture”)

crydd (“cobbler”) + -aniaeth → cryddaniaeth (“shoemaking”)

brwd (“enthusiastic”) + -aniaeth → brwdaniaeth (“fervour”)

drud (“expensive”) + -aniaeth → drudaniaeth (“costliness”)


-iaidd

From Middle Welsh -eid, from Proto-Celtic *‑adi̯os. Cognate with Old Irish -de, Greek -άδα (-áda), Latin -idus.

llun (“shape, form”) + -iaidd → lluniaidd (“shapely, well-formed”)

dewin (“wizard”) + -iaidd → dewiniaidd (“divinatory”)


-áu

creates a verbal noun from an adjectival root


gwes

Proto-Indo-European *h₂wes- (“to dwell, stay”)

forms nouns with connotations of comfort and shelter


-oleg

sw (“zoo”) + -oleg → swoleg (“zoology”)


-öig

(organic chemistry) -oic (suffix denoting carboxylic groups)