"-ա-" meaning in Old Armenian

{
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "axm",
            "2": "-ա-"
          },
          "expansion": "Middle Armenian: -ա- (-a-)\nArmenian: -ա- (-a-)",
          "name": "desctree"
        }
      ],
      "text": "Middle Armenian: -ա- (-a-)\nArmenian: -ա- (-a-)"
    }
  ],
  "forms": [
    {
      "form": "-a-",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "xcl",
        "2": "interfix"
      },
      "expansion": "-ա- • (-a-)",
      "name": "head"
    }
  ],
  "lang": "Old Armenian",
  "lang_code": "xcl",
  "pos": "interfix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Old Armenian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Old Armenian interfixes",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "ծայր-ա-քաղաք ― cayr-a-kʻałakʻ ― acropolis",
          "type": "example"
        }
      ],
      "glosses": [
        "an agglutinating interfix"
      ],
      "id": "en--ա--xcl-interfix-ebp3Kyi3",
      "tags": [
        "morpheme"
      ]
    }
  ],
  "word": "-ա-"
}

{
  "descendants": [
    {
      "depth": 1,
      "templates": [
        {
          "args": {
            "1": "axm",
            "2": "-ա-"
          },
          "expansion": "Middle Armenian: -ա- (-a-)\nArmenian: -ա- (-a-)",
          "name": "desctree"
        }
      ],
      "text": "Middle Armenian: -ա- (-a-)\nArmenian: -ա- (-a-)"
    }
  ],
  "forms": [
    {
      "form": "-a-",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "xcl",
        "2": "interfix"
      },
      "expansion": "-ա- • (-a-)",
      "name": "head"
    }
  ],
  "lang": "Old Armenian",
  "lang_code": "xcl",
  "pos": "interfix",
  "senses": [
    {
      "categories": [
        "Old Armenian entries with incorrect language header",
        "Old Armenian interfixes",
        "Old Armenian lemmas",
        "Old Armenian terms with usage examples"
      ],
      "examples": [
        {
          "text": "ծայր-ա-քաղաք ― cayr-a-kʻałakʻ ― acropolis",
          "type": "example"
        }
      ],
      "glosses": [
        "an agglutinating interfix"
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "word": "-ա-"
}