English Example: The word "unbelievable" has three morphemes "un-" meaning "non-", "-believe-", and "-able". "un-" is a prefix morpheme, "-able" is a suffix morpheme. Both are affixes.
Types of morphemes: Bound morphemes like a- appear only together with other morphemes to form a lexeme. Free morphemes like town can appear with other lexemes (town-hall) and alone. Allomorphs are variants of a morpheme, e.g. the plural marker in English is sometimes realized as /-z/, /-s/ or /-Iz/.
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