"father-bother merger" meaning in English

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      "expansion": "father-bother merger",
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  "lang_code": "en",
  "pos": "noun",
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          "ref": "2018, Gregory H. Bontrager, “Ambisyllabicity in an Optimal-Theoretic Model of English Stress Assignment”, in Florida Linguistics Papers, volume 5, number 2",
          "text": "The first is the father-bother merger, a loss of rounding contrast in the low back vowels by which the originally contrastive /ɒ/ has been subsumed by /ɑː/ into the fused phoneme /ɑ/.",
          "type": "quotation"
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      "glosses": [
        "A phonemic merger in English of the vowels /ɑː/ (as in father) and /ɒ/ (as in bother)."
      ],
      "id": "en-father-bother_merger-en-noun-ejqgwCTX",
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        [
          "vowel",
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        ],
        [
          "father",
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        ],
        [
          "bother",
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        ]
      ],
      "related": [
        {
          "word": "cot-caught merger"
        }
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      "wikipedia": [
        "father-bother merger"
      ]
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  "sounds": [
    {
      "ipa": "/ˌfɑːðə ˈbɒðə ˈmɜːdʒə(ɹ)/",
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      "ipa": "/ˌfɑðɚ ˈbɑðɚ ˈmɝdʒɚ/",
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    }
  ],
  "word": "father-bother merger"
}

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  "lang_code": "en",
  "pos": "noun",
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    {
      "word": "cot-caught merger"
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        "A phonemic merger in English of the vowels /ɑː/ (as in father) and /ɒ/ (as in bother)."
      ],
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          "phonemic merger",
          "phonemic merger"
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  "sounds": [
    {
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  "word": "father-bother merger"
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