suppletion

English Wikipedia has an article on:

suppletion

Wikipedia

From German Suppletivwesen, from Latin supplēre (“to supply”), perfect stem supplet-, + -ion.

• IPA^(key): /səˈpliːʃən/

suppletion (usually uncountable, plural suppletions)

1. The supplying of something lacking.

   Coordinate terms: supplementation; repletion; completion; augmentation

2. (linguistics, grammar) The use of an unrelated word or phrase to supply inflected forms otherwise lacking, e.g. using “to be able” as the infinitive of “can”, or “better” as the comparative of “good”, or “went” as the simple past of “go”.
3. (grammar) More loosely, the use of unrelated (or distantly related) words for semantically related words which may not share the same lexical category, such as father/paternal or cow/bovine, normally referred to as collateral adjectives.

Strictly speaking, suppletion in linguistics refers only to inflection, such as good / better, which are both adjectives, and this is the most frequent use. It is also used in the looser sense of semantic relations without etymological relations (or with distant etymological relations) such as father / paternal, where these are noun/adjective.^[1][2] However, this latter use is significantly less common and may be considered incorrect. The term suppletion is particularly used to contrast these phenomena with phonologically conditioned irregularities like man / men, where both parts are derived by sound changes from an originally regular paradigm.

• noncognate