a morpheme is the smallest meaningful unit in a word. e,g. cat is a free morpheme unhappy consists of two morphemes : a free morpheme ( happy)and a bound morpheme (un) An allomorph is one of two or more complementary morphs which manifest a morpheme in its different phonological or morphological environments. for example the plural 's' has three allomorphs /s/ cats /z/ dogs /iz/ buses also the ir/il/un/im are allomorphs for the negative

allomorph = any of the variant forms of a morpheme. For example, the phonetic (s) of cats (kts), (z) of pigs (pgz), and (z) horses (hôrsz) are allomorphs of the English plural morpheme.