An ELT Glossary : Allomorphs

  • Definition : a variant of a morpheme (the smallest possible part of a word that has meaning).
  • 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, (cups) -es (buses), and -en (oxen).
  • Allomorphs are not interchangeable - ie we can't say *unpossible,  * oxes or *cupen.