"летен" meaning in Russian

{
  "forms": [
    {
      "form": "ле́тен",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "léten",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ru",
        "2": "adjective form",
        "head": "ле́тен"
      },
      "expansion": "ле́тен • (léten)",
      "name": "head"
    }
  ],
  "lang": "Russian",
  "lang_code": "ru",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 3 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Russian entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "form_of": [
        {
          "extra": "létnyj",
          "word": "ле́тный"
        }
      ],
      "glosses": [
        "short masculine singular of ле́тный (létnyj)"
      ],
      "id": "en-летен-ru-adj-gZyx4YII",
      "links": [
        [
          "ле́тный",
          "летный#Russian"
        ]
      ],
      "tags": [
        "form-of",
        "masculine",
        "short-form",
        "singular"
      ]
    }
  ],
  "word": "летен"
}

{
  "forms": [
    {
      "form": "ле́тен",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "léten",
      "tags": [
        "romanization"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "ru",
        "2": "adjective form",
        "head": "ле́тен"
      },
      "expansion": "ле́тен • (léten)",
      "name": "head"
    }
  ],
  "lang": "Russian",
  "lang_code": "ru",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "Pages with 3 entries",
        "Pages with entries",
        "Russian adjective forms",
        "Russian entries with incorrect language header",
        "Russian non-lemma forms"
      ],
      "form_of": [
        {
          "extra": "létnyj",
          "word": "ле́тный"
        }
      ],
      "glosses": [
        "short masculine singular of ле́тный (létnyj)"
      ],
      "links": [
        [
          "ле́тный",
          "летный#Russian"
        ]
      ],
      "tags": [
        "form-of",
        "masculine",
        "short-form",
        "singular"
      ]
    }
  ],
  "word": "летен"
}