"reäction" meaning in English

{
  "etymology_text": "The diaeresis emphasizes the pronunciation of the word with three rather than two syllables.",
  "forms": [
    {
      "form": "reäctions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "reäction (plural reäctions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "reaction"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English terms with non-redundant non-automated sortkeys",
          "parents": [
            "Terms with non-redundant non-automated sortkeys",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Rare spelling of reaction."
      ],
      "id": "en-reäction-en-noun-IjlHLbDJ",
      "links": [
        [
          "reaction",
          "reaction#English"
        ]
      ],
      "tags": [
        "alt-of",
        "rare"
      ]
    }
  ],
  "word": "reäction"
}

{
  "etymology_text": "The diaeresis emphasizes the pronunciation of the word with three rather than two syllables.",
  "forms": [
    {
      "form": "reäctions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "reäction (plural reäctions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "reaction"
        }
      ],
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English nouns",
        "English rare forms",
        "English terms spelled with Ä",
        "English terms spelled with ◌̈",
        "English terms with non-redundant non-automated sortkeys",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Rare spelling of reaction."
      ],
      "links": [
        [
          "reaction",
          "reaction#English"
        ]
      ],
      "tags": [
        "alt-of",
        "rare"
      ]
    }
  ],
  "word": "reäction"
}