suppletion

/səˈpliʃən/
noun
  1. The use of an unrelated word to fill a gap in a grammatical pattern, such as using 'went' as the past tense of 'go'.
    • In English, the word 'better' is an example of suppletion because it is not formed from 'good'.
    • The suppletion of 'be' with 'am', 'is', and 'are' shows how verbs can change completely.
    • Linguistics students study suppletion to understand how languages handle irregular forms.
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