"-u-" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "human"
      },
      "expansion": "human",
      "name": "m"
    }
  ],
  "etymology_text": "From the initial vowel of human.",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "infix"
      },
      "expansion": "-u-",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "infix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English infixes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Pharmacology",
          "orig": "en:Pharmacology",
          "parents": [
            "Biochemistry",
            "Medicine",
            "Biology",
            "Chemistry",
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "a monoclonal antibody derived from a human source."
      ],
      "id": "en--u--en-infix-BC9Nba9D",
      "links": [
        [
          "pharmacology",
          "pharmacology"
        ],
        [
          "monoclonal antibody",
          "monoclonal antibody"
        ],
        [
          "human",
          "human"
        ]
      ],
      "raw_glosses": [
        "(pharmacology) a monoclonal antibody derived from a human source."
      ],
      "related": [
        {
          "english": "See that entry for full paradigm.",
          "word": "-mab is the base suffix common to all monoclonal antibodies"
        }
      ],
      "tags": [
        "morpheme"
      ],
      "topics": [
        "medicine",
        "pharmacology",
        "sciences"
      ]
    }
  ],
  "word": "-u-"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "human"
      },
      "expansion": "human",
      "name": "m"
    }
  ],
  "etymology_text": "From the initial vowel of human.",
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "infix"
      },
      "expansion": "-u-",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "infix",
  "related": [
    {
      "english": "See that entry for full paradigm.",
      "word": "-mab is the base suffix common to all monoclonal antibodies"
    }
  ],
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English infixes",
        "English lemmas",
        "en:Pharmacology"
      ],
      "glosses": [
        "a monoclonal antibody derived from a human source."
      ],
      "links": [
        [
          "pharmacology",
          "pharmacology"
        ],
        [
          "monoclonal antibody",
          "monoclonal antibody"
        ],
        [
          "human",
          "human"
        ]
      ],
      "raw_glosses": [
        "(pharmacology) a monoclonal antibody derived from a human source."
      ],
      "tags": [
        "morpheme"
      ],
      "topics": [
        "medicine",
        "pharmacology",
        "sciences"
      ]
    }
  ],
  "word": "-u-"
}