"de-" meaning in Breton

{
  "categories": [
    {
      "kind": "other",
      "name": "Préfixes en breton",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Breton",
      "orig": "breton",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Breton",
  "lang_code": "br",
  "pos": "prefix",
  "pos_title": "Préfixe",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Exemples en breton",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Exemples en breton à traduire",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "kas, degas."
        },
        {
          "text": "redek, deredek."
        },
        {
          "text": "sevel, desevel."
        }
      ],
      "glosses": [
        "Préfixe indiquant un rapprochement et provoquant une mutation par adoucissement"
      ],
      "id": "fr-de--br-prefix-jJGGyaOm"
    }
  ],
  "tags": [
    "morpheme"
  ],
  "word": "de-"
}

{
  "categories": [
    "Préfixes en breton",
    "breton"
  ],
  "lang": "Breton",
  "lang_code": "br",
  "pos": "prefix",
  "pos_title": "Préfixe",
  "senses": [
    {
      "categories": [
        "Exemples en breton",
        "Exemples en breton à traduire"
      ],
      "examples": [
        {
          "text": "kas, degas."
        },
        {
          "text": "redek, deredek."
        },
        {
          "text": "sevel, desevel."
        }
      ],
      "glosses": [
        "Préfixe indiquant un rapprochement et provoquant une mutation par adoucissement"
      ]
    }
  ],
  "tags": [
    "morpheme"
  ],
  "word": "de-"
}