morpheme: small part of a word that adds meaning e.g. in the word "unattractive", 'un-' is the morpheme. morphemes cant be broken up into smaller words, as they are small words of few letters.
allophones: the same phonemes (pieces of sound) pronounced differently, e.g. 'p' in 'pin' is not aspirated, but 'p' in 'spin' IS asiprated
allomorphs: morphemes that vary in sound, but not meaning e.g. 'fished' ('ed' is the morpheme- it sounds like 't' when added to 'fish' to make 'fished,' but alone sounds like 'ed', like short for the name Edward)
hope this helped!!