"-iff" meaning in All languages combined

{
  "head_templates": [
    {
      "args": {
        "1": "cy",
        "2": "suffix"
      },
      "expansion": "-iff",
      "name": "head"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages using catfix",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "South Wales Welsh",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Welsh entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "verb suffix for the third-person singular future"
      ],
      "id": "en--iff-cy-suffix-9vHzdLGe",
      "links": [
        [
          "third-person",
          "third person#English"
        ],
        [
          "singular",
          "singular#English"
        ],
        [
          "future",
          "future#English"
        ]
      ],
      "raw_glosses": [
        "(South Wales, colloquial) verb suffix for the third-person singular future"
      ],
      "synonyms": [
        {
          "word": "-ith"
        }
      ],
      "tags": [
        "South-Wales",
        "colloquial",
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɪf/"
    }
  ],
  "word": "-iff"
}

{
  "head_templates": [
    {
      "args": {
        "1": "cy",
        "2": "suffix"
      },
      "expansion": "-iff",
      "name": "head"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        "Pages using catfix",
        "Pages with 1 entry",
        "Pages with entries",
        "South Wales Welsh",
        "Welsh colloquialisms",
        "Welsh entries with incorrect language header",
        "Welsh lemmas",
        "Welsh suffixes"
      ],
      "glosses": [
        "verb suffix for the third-person singular future"
      ],
      "links": [
        [
          "third-person",
          "third person#English"
        ],
        [
          "singular",
          "singular#English"
        ],
        [
          "future",
          "future#English"
        ]
      ],
      "raw_glosses": [
        "(South Wales, colloquial) verb suffix for the third-person singular future"
      ],
      "tags": [
        "South-Wales",
        "colloquial",
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɪf/"
    }
  ],
  "synonyms": [
    {
      "word": "-ith"
    }
  ],
  "word": "-iff"
}