"юнъ" meaning in Vieux slave

{
  "antonyms": [
    {
      "word": "старъ"
    }
  ],
  "categories": [
    {
      "kind": "other",
      "name": "Adjectifs en vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Mots en vieux slave issus d’un mot en proto-slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Vieux slave",
      "orig": "vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Étymologies en vieux slave incluant une reconstruction",
      "parents": [],
      "source": "w"
    }
  ],
  "derived": [
    {
      "word": "юница"
    },
    {
      "word": "юность"
    },
    {
      "word": "юнота"
    },
    {
      "word": "юнотьнъ"
    },
    {
      "word": "юноша"
    },
    {
      "word": "юньць"
    },
    {
      "word": "юньчь"
    }
  ],
  "etymology_texts": [
    "Du proto-slave *jūnъ."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "adj",
  "pos_title": "Adjectif",
  "senses": [
    {
      "glosses": [
        "Jeune."
      ],
      "id": "fr-юнъ-cu-adj-8zVBhYF6"
    }
  ],
  "word": "юнъ"
}

{
  "antonyms": [
    {
      "word": "старъ"
    }
  ],
  "categories": [
    "Adjectifs en vieux slave",
    "Mots en vieux slave issus d’un mot en proto-slave",
    "vieux slave",
    "Étymologies en vieux slave incluant une reconstruction"
  ],
  "derived": [
    {
      "word": "юница"
    },
    {
      "word": "юность"
    },
    {
      "word": "юнота"
    },
    {
      "word": "юнотьнъ"
    },
    {
      "word": "юноша"
    },
    {
      "word": "юньць"
    },
    {
      "word": "юньчь"
    }
  ],
  "etymology_texts": [
    "Du proto-slave *jūnъ."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "adj",
  "pos_title": "Adjectif",
  "senses": [
    {
      "glosses": [
        "Jeune."
      ]
    }
  ],
  "word": "юнъ"
}