"-tsu" meaning in Basque

{
  "head_templates": [
    {
      "args": {
        "1": "eu",
        "2": "suffix"
      },
      "expansion": "-tsu",
      "name": "head"
    }
  ],
  "lang": "Basque",
  "lang_code": "eu",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Basque entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "eguzki (“sun”) + -tsu → eguzkitsu (“sunny”)",
          "type": "example"
        },
        {
          "text": "euri (“rain”) + -tsu → euritsu (“rainy”)",
          "type": "example"
        }
      ],
      "glosses": [
        "Used to create adjectives from nouns."
      ],
      "id": "en--tsu-eu-suffix-NS~7hXKV",
      "tags": [
        "morpheme"
      ]
    }
  ],
  "word": "-tsu"
}

{
  "head_templates": [
    {
      "args": {
        "1": "eu",
        "2": "suffix"
      },
      "expansion": "-tsu",
      "name": "head"
    }
  ],
  "lang": "Basque",
  "lang_code": "eu",
  "pos": "suffix",
  "senses": [
    {
      "categories": [
        "Basque entries with incorrect language header",
        "Basque lemmas",
        "Basque suffixes"
      ],
      "examples": [
        {
          "text": "eguzki (“sun”) + -tsu → eguzkitsu (“sunny”)",
          "type": "example"
        },
        {
          "text": "euri (“rain”) + -tsu → euritsu (“rainy”)",
          "type": "example"
        }
      ],
      "glosses": [
        "Used to create adjectives from nouns."
      ],
      "tags": [
        "morpheme"
      ]
    }
  ],
  "word": "-tsu"
}