"lunate sigma" meaning in English

{
  "forms": [
    {
      "form": "lunate sigmas",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
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      "args": {},
      "expansion": "lunate sigma (plural lunate sigmas)",
      "name": "en-noun"
    }
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
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          "kind": "other",
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          "source": "w"
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        {
          "kind": "topical",
          "langcode": "en",
          "name": "Greek letter names",
          "orig": "en:Greek letter names",
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            "Letters, symbols, and punctuation",
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        }
      ],
      "glosses": [
        "The form of the Greek letter sigma used in Medieval Greek and occasionally in Greek Orthodox Church transcriptions: ϲ."
      ],
      "id": "en-lunate_sigma-en-noun-Od5x9SKK",
      "links": [
        [
          "Greek",
          "Greek"
        ],
        [
          "Medieval Greek",
          "Medieval Greek"
        ],
        [
          "ϲ",
          "ϲ"
        ]
      ],
      "related": [
        {
          "word": "final sigma"
        }
      ],
      "wikipedia": [
        "lunate sigma"
      ]
    }
  ],
  "word": "lunate sigma"
}

{
  "forms": [
    {
      "form": "lunate sigmas",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "lunate sigma (plural lunate sigmas)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "final sigma"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
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        "English multiword terms",
        "English nouns",
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        "Pages with entries",
        "en:Greek letter names"
      ],
      "glosses": [
        "The form of the Greek letter sigma used in Medieval Greek and occasionally in Greek Orthodox Church transcriptions: ϲ."
      ],
      "links": [
        [
          "Greek",
          "Greek"
        ],
        [
          "Medieval Greek",
          "Medieval Greek"
        ],
        [
          "ϲ",
          "ϲ"
        ]
      ],
      "wikipedia": [
        "lunate sigma"
      ]
    }
  ],
  "word": "lunate sigma"
}