In linguistics and etymology, suppletion is traditionally understood as the use of one word as the inflected form of another word when the two words are not cognate. For those learning a language, suppletive forms will be seen as "irregular"or even "highly irregular".

SUPPLETION
Suppletion
Suppletion
Saul Levin
Universals in Comparative Morphology: Suppletion, Superlatives, and the Structure of Words
Universals in comparative morphology : suppletion, superlatives, and the structure of words
Canonical Typolgy, Suppletion, and Possible Words
Suppletion in the old basque verb "to give": a typological perspective
Suppletion and Dependency in Inflectional Morphology
Some implications of phonologically conditioned suppletion
When lexemes become allomorphs - On the genesis of suppletion
Chapter 8. Suppletion : Aspects of the Theory of Morphology
Suppletion in Verb Paradigms: Bits and Pieces of a Puzzle