allomorph
Linguistics term for a variant phonetic form of a morpheme that occurs in a specific phonological or morphological context.
異形態は同じ形態素の異なる形です。
Allomorphs are different forms of the same morpheme.
Compound of 異 (i, 'different') + 形態 (keitai, 'form'), likely a calque from English 'allomorph'.