"U15" meaning in Translingual

{
  "etymology_templates": [
    {
      "args": {
        "1": "mul",
        "2": "under 15"
      },
      "expansion": "Abbreviation of under 15.",
      "name": "abbreviation of"
    },
    {
      "args": {
        "1": "mul",
        "2": "en",
        "3": "-"
      },
      "expansion": "English",
      "name": "der"
    }
  ],
  "etymology_text": "Abbreviation of under 15. From English",
  "head_templates": [
    {
      "args": {
        "1": "mul",
        "2": "adjective"
      },
      "expansion": "U15",
      "name": "head"
    }
  ],
  "lang": "Translingual",
  "lang_code": "mul",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Translingual entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "mul",
          "name": "Sports",
          "orig": "mul:Sports",
          "parents": [
            "Human activity",
            "Human behaviour",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "coordinate_terms": [
        {
          "word": "U16"
        },
        {
          "word": "U17"
        },
        {
          "word": "U18"
        },
        {
          "word": "U20"
        },
        {
          "word": "U21"
        }
      ],
      "glosses": [
        "pertaining to a grouping of people who are under 15 years of age"
      ],
      "id": "en-U15-mul-adj-Pmqt61xk",
      "links": [
        [
          "sports",
          "sports"
        ]
      ],
      "raw_glosses": [
        "(sports) pertaining to a grouping of people who are under 15 years of age"
      ],
      "synonyms": [
        {
          "word": "U-15"
        }
      ],
      "topics": [
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "U15"
}

{
  "coordinate_terms": [
    {
      "word": "U16"
    },
    {
      "word": "U17"
    },
    {
      "word": "U18"
    },
    {
      "word": "U20"
    },
    {
      "word": "U21"
    }
  ],
  "etymology_templates": [
    {
      "args": {
        "1": "mul",
        "2": "under 15"
      },
      "expansion": "Abbreviation of under 15.",
      "name": "abbreviation of"
    },
    {
      "args": {
        "1": "mul",
        "2": "en",
        "3": "-"
      },
      "expansion": "English",
      "name": "der"
    }
  ],
  "etymology_text": "Abbreviation of under 15. From English",
  "head_templates": [
    {
      "args": {
        "1": "mul",
        "2": "adjective"
      },
      "expansion": "U15",
      "name": "head"
    }
  ],
  "lang": "Translingual",
  "lang_code": "mul",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Translingual abbreviations",
        "Translingual adjectives",
        "Translingual entries with incorrect language header",
        "Translingual lemmas",
        "Translingual terms derived from English",
        "Translingual terms spelled with numbers",
        "mul:Sports"
      ],
      "glosses": [
        "pertaining to a grouping of people who are under 15 years of age"
      ],
      "links": [
        [
          "sports",
          "sports"
        ]
      ],
      "raw_glosses": [
        "(sports) pertaining to a grouping of people who are under 15 years of age"
      ],
      "topics": [
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "U-15"
    }
  ],
  "word": "U15"
}