An ELT Glossary : Allomorphs

  • Definition : a variant of a morpheme.

  • Examples : un- in- il- im- and ir- are all variants of the negative adjective prefix and therefore allomorphs. Similarly long and leng-, strong and streng- (as in length, strength), and the noun plural endings -s, es, and -en.

  • Allomorphs are not interchangeable - ie we can't say *unpossible, *longth or *busen.