"εἰ" meaning in Ancient Greek

{
  "etymology_templates": [
    {
      "args": {
        "1": "grc",
        "2": "ine-pro",
        "3": "*éy"
      },
      "expansion": "Proto-Indo-European *éy",
      "name": "der"
    },
    {
      "args": {
        "1": "grc",
        "2": "ἐπεί"
      },
      "expansion": "ἐπεί (epeí)",
      "name": "m"
    },
    {
      "args": {
        "1": "la",
        "2": "sī"
      },
      "expansion": "sī",
      "name": "m"
    }
  ],
  "etymology_text": "From Proto-Indo-European *éy. See its sense, “that”, in ἐπεί (epeí) and compare the history of Latin sī.",
  "forms": [
    {
      "form": "ei",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "grc",
        "2": "conjunction",
        "cat2": "subordinating conjunctions",
        "head": "",
        "head2": ""
      },
      "expansion": "εἰ • (ei)",
      "name": "head"
    },
    {
      "args": {
        "1": "",
        "2": "s"
      },
      "expansion": "εἰ • (ei)",
      "name": "grc-conjunction"
    }
  ],
  "lang": "Ancient Greek",
  "lang_code": "grc",
  "pos": "conj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Ancient Greek entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "derived": [
        {
          "roman": "eíthe",
          "word": "εἴθε"
        },
        {
          "roman": "eîta",
          "word": "εἶτα"
        },
        {
          "roman": "epeí",
          "word": "ἐπεί"
        }
      ],
      "glosses": [
        "if"
      ],
      "id": "en-εἰ-grc-conj-k19oMZ1P",
      "links": [
        [
          "if",
          "if"
        ]
      ],
      "synonyms": [
        {
          "roman": "ai",
          "tags": [
            "Doric"
          ],
          "word": "αἰ"
        },
        {
          "word": "Epic"
        },
        {
          "roman": "eí",
          "tags": [
            "stressed"
          ],
          "word": "εἴ"
        },
        {
          "english": "before a word starting with a vowel",
          "roman": "eik",
          "word": "εἰκ"
        }
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/eː/"
    },
    {
      "ipa": "/i/"
    },
    {
      "ipa": "/i/"
    },
    {
      "ipa": "/eː/",
      "note": "5ᵗʰ BCE Attic"
    },
    {
      "ipa": "/i/",
      "note": "1ˢᵗ CE Egyptian"
    },
    {
      "ipa": "/i/",
      "note": "4ᵗʰ CE Koine"
    },
    {
      "ipa": "/i/",
      "note": "10ᵗʰ CE Byzantine"
    },
    {
      "ipa": "/i/",
      "note": "15ᵗʰ CE Constantinopolitan"
    }
  ],
  "word": "εἰ"
}

{
  "derived": [
    {
      "roman": "eíthe",
      "word": "εἴθε"
    },
    {
      "roman": "eîta",
      "word": "εἶτα"
    },
    {
      "roman": "epeí",
      "word": "ἐπεί"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "grc",
        "2": "ine-pro",
        "3": "*éy"
      },
      "expansion": "Proto-Indo-European *éy",
      "name": "der"
    },
    {
      "args": {
        "1": "grc",
        "2": "ἐπεί"
      },
      "expansion": "ἐπεί (epeí)",
      "name": "m"
    },
    {
      "args": {
        "1": "la",
        "2": "sī"
      },
      "expansion": "sī",
      "name": "m"
    }
  ],
  "etymology_text": "From Proto-Indo-European *éy. See its sense, “that”, in ἐπεί (epeí) and compare the history of Latin sī.",
  "forms": [
    {
      "form": "ei",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "grc",
        "2": "conjunction",
        "cat2": "subordinating conjunctions",
        "head": "",
        "head2": ""
      },
      "expansion": "εἰ • (ei)",
      "name": "head"
    },
    {
      "args": {
        "1": "",
        "2": "s"
      },
      "expansion": "εἰ • (ei)",
      "name": "grc-conjunction"
    }
  ],
  "lang": "Ancient Greek",
  "lang_code": "grc",
  "pos": "conj",
  "senses": [
    {
      "categories": [
        "Ancient Greek 1-syllable words",
        "Ancient Greek conjunctions",
        "Ancient Greek entries with incorrect language header",
        "Ancient Greek lemmas",
        "Ancient Greek subordinating conjunctions",
        "Ancient Greek terms derived from Proto-Indo-European",
        "Ancient Greek terms with IPA pronunciation"
      ],
      "glosses": [
        "if"
      ],
      "links": [
        [
          "if",
          "if"
        ]
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/eː/"
    },
    {
      "ipa": "/i/"
    },
    {
      "ipa": "/i/"
    },
    {
      "ipa": "/eː/",
      "note": "5ᵗʰ BCE Attic"
    },
    {
      "ipa": "/i/",
      "note": "1ˢᵗ CE Egyptian"
    },
    {
      "ipa": "/i/",
      "note": "4ᵗʰ CE Koine"
    },
    {
      "ipa": "/i/",
      "note": "10ᵗʰ CE Byzantine"
    },
    {
      "ipa": "/i/",
      "note": "15ᵗʰ CE Constantinopolitan"
    }
  ],
  "synonyms": [
    {
      "roman": "ai",
      "tags": [
        "Doric"
      ],
      "word": "αἰ"
    },
    {
      "word": "Epic"
    },
    {
      "roman": "eí",
      "tags": [
        "stressed"
      ],
      "word": "εἴ"
    },
    {
      "english": "before a word starting with a vowel",
      "roman": "eik",
      "word": "εἰκ"
    }
  ],
  "word": "εἰ"
}