1) The irregular plurals like men, mice, children, oxen, sheep, deer;2) The past form and /or- ed participle of certain verbs like went, came, took, cut;3) The irregular comparatives and superlatives like better, best, further, furthest.However, a morpheme may undergo certain phonetic changes when combined with the base word .For example, the plural morpheme s is pronounced [z] in dogs, [s]in pests, and [iz]in houses .The different variants of a morpheme are called allomorphs .