"a-" meaning in Irish

{
  "etymology_number": 1,
  "etymology_templates": [
    {
      "args": {
        "1": "ga",
        "2": "grc",
        "3": "ἀ-"
      },
      "expansion": "Ancient Greek ἀ- (a-)",
      "name": "bor"
    }
  ],
  "etymology_text": "From Ancient Greek ἀ- (a-) (ἀν- (an-) immediately followed by a vowel).",
  "forms": [
    {
      "form": "ai-",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ga",
        "2": "prefix"
      },
      "expansion": "a-",
      "name": "head"
    }
  ],
  "lang": "Irish",
  "lang_code": "ga",
  "pos": "prefix",
  "senses": [
    {
      "glosses": [
        "a- (not, without, opposite of)"
      ],
      "id": "en-a--ga-prefix-z3HWu~hB",
      "links": [
        [
          "a-",
          "#English"
        ]
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/a/"
    },
    {
      "ipa": "/a/"
    },
    {
      "ipa": "/ə/"
    }
  ],
  "word": "a-"
}

{
  "etymology_number": 2,
  "forms": [
    {
      "form": "ai-",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ga",
        "2": "prefix"
      },
      "expansion": "a-",
      "name": "head"
    }
  ],
  "lang": "Irish",
  "lang_code": "ga",
  "pos": "prefix",
  "senses": [
    {
      "alt_of": [
        {
          "word": "ath- used before t"
        }
      ],
      "categories": [
        {
          "_dis": "14 86",
          "kind": "other",
          "name": "Irish entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w+disamb"
        }
      ],
      "glosses": [
        "Alternative form of ath- used before t"
      ],
      "id": "en-a--ga-prefix-RXqRKwCw",
      "links": [
        [
          "ath-",
          "ath-#Irish"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/a/"
    },
    {
      "ipa": "/ə/"
    }
  ],
  "word": "a-"
}

{
  "categories": [
    "Irish entries with incorrect language header",
    "Irish lemmas",
    "Irish prefixes",
    "Irish terms borrowed from Ancient Greek",
    "Irish terms derived from Ancient Greek",
    "Pages using catfix",
    "Pages with 52 entries",
    "Pages with entries"
  ],
  "etymology_number": 1,
  "etymology_templates": [
    {
      "args": {
        "1": "ga",
        "2": "grc",
        "3": "ἀ-"
      },
      "expansion": "Ancient Greek ἀ- (a-)",
      "name": "bor"
    }
  ],
  "etymology_text": "From Ancient Greek ἀ- (a-) (ἀν- (an-) immediately followed by a vowel).",
  "forms": [
    {
      "form": "ai-",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ga",
        "2": "prefix"
      },
      "expansion": "a-",
      "name": "head"
    }
  ],
  "lang": "Irish",
  "lang_code": "ga",
  "pos": "prefix",
  "senses": [
    {
      "glosses": [
        "a- (not, without, opposite of)"
      ],
      "links": [
        [
          "a-",
          "#English"
        ]
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/a/"
    },
    {
      "ipa": "/a/"
    },
    {
      "ipa": "/ə/"
    }
  ],
  "word": "a-"
}

{
  "categories": [
    "Irish entries with incorrect language header",
    "Irish lemmas",
    "Irish prefixes",
    "Pages with 52 entries",
    "Pages with entries"
  ],
  "etymology_number": 2,
  "forms": [
    {
      "form": "ai-",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ga",
        "2": "prefix"
      },
      "expansion": "a-",
      "name": "head"
    }
  ],
  "lang": "Irish",
  "lang_code": "ga",
  "pos": "prefix",
  "senses": [
    {
      "alt_of": [
        {
          "word": "ath- used before t"
        }
      ],
      "glosses": [
        "Alternative form of ath- used before t"
      ],
      "links": [
        [
          "ath-",
          "ath-#Irish"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "morpheme"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/a/"
    },
    {
      "ipa": "/ə/"
    }
  ],
  "word": "a-"
}