What is an allomorph?

Question: What is an allophorph? give examples for illustration

An allophorph is any variants of a morpheme which is different in pronunciation or spelling

Eg: “a”, “an” – “an” is an allomorph of “a”

“s” – “es” . “s”: /z/, /iz/ are allomorphs

“ed”: /t/, /d/,/id/