"opt in" meaning in English

{
  "antonyms": [
    {
      "word": "opt out"
    }
  ],
  "etymology_text": "From opt + in.",
  "forms": [
    {
      "form": "opts in",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "opting in",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "opted in",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "opted in",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "opt in (third-person singular simple present opts in, present participle opting in, simple past and past participle opted in)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "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 phrasal verbs formed with \"in\"",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Entries with translation boxes",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Finnish translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with French translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with German translations",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Terms with Russian translations",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "To choose to participate in something"
      ],
      "id": "en-opt_in-en-verb-mfIOMpuR",
      "links": [
        [
          "choose",
          "choose"
        ],
        [
          "participate",
          "participate"
        ]
      ],
      "translations": [
        {
          "code": "fi",
          "lang": "Finnish",
          "sense": "To choose to participate in something",
          "word": "päättää osallistua"
        },
        {
          "code": "fi",
          "lang": "Finnish",
          "sense": "To choose to participate in something",
          "word": "ilmoittautua"
        },
        {
          "code": "fi",
          "lang": "Finnish",
          "sense": "To choose to participate in something",
          "word": "osallistua"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "To choose to participate in something",
          "word": "opter"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "To choose to participate in something",
          "word": "consentir"
        },
        {
          "code": "de",
          "lang": "German",
          "sense": "To choose to participate in something",
          "word": "hineinoptieren"
        },
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "učástvovatʹ",
          "sense": "To choose to participate in something",
          "word": "уча́ствовать"
        },
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "prisojedinjátʹsja",
          "sense": "To choose to participate in something",
          "word": "присоединя́ться"
        }
      ]
    }
  ],
  "word": "opt in"
}

{
  "antonyms": [
    {
      "word": "opt out"
    }
  ],
  "etymology_text": "From opt + in.",
  "forms": [
    {
      "form": "opts in",
      "tags": [
        "present",
        "singular",
        "third-person"
      ]
    },
    {
      "form": "opting in",
      "tags": [
        "participle",
        "present"
      ]
    },
    {
      "form": "opted in",
      "tags": [
        "participle",
        "past"
      ]
    },
    {
      "form": "opted in",
      "tags": [
        "past"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "*"
      },
      "expansion": "opt in (third-person singular simple present opts in, present participle opting in, simple past and past participle opted in)",
      "name": "en-verb"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "verb",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English phrasal verbs",
        "English phrasal verbs formed with \"in\"",
        "English verbs",
        "Entries with translation boxes",
        "Pages with 1 entry",
        "Pages with entries",
        "Terms with Finnish translations",
        "Terms with French translations",
        "Terms with German translations",
        "Terms with Russian translations"
      ],
      "glosses": [
        "To choose to participate in something"
      ],
      "links": [
        [
          "choose",
          "choose"
        ],
        [
          "participate",
          "participate"
        ]
      ]
    }
  ],
  "translations": [
    {
      "code": "fi",
      "lang": "Finnish",
      "sense": "To choose to participate in something",
      "word": "päättää osallistua"
    },
    {
      "code": "fi",
      "lang": "Finnish",
      "sense": "To choose to participate in something",
      "word": "ilmoittautua"
    },
    {
      "code": "fi",
      "lang": "Finnish",
      "sense": "To choose to participate in something",
      "word": "osallistua"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "To choose to participate in something",
      "word": "opter"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "To choose to participate in something",
      "word": "consentir"
    },
    {
      "code": "de",
      "lang": "German",
      "sense": "To choose to participate in something",
      "word": "hineinoptieren"
    },
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "učástvovatʹ",
      "sense": "To choose to participate in something",
      "word": "уча́ствовать"
    },
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "prisojedinjátʹsja",
      "sense": "To choose to participate in something",
      "word": "присоединя́ться"
    }
  ],
  "word": "opt in"
}