This document discusses key concepts in morphology including: 1. Morphemes are the smallest units of meaning in a language. There are two types: free morphemes which can stand alone as words, and bound morphemes which cannot stand alone and include prefixes and suffixes. 2. Morphs are the actual forms used to realize morphemes. Allomorphs are variant forms of the same morpheme. 3. Phonemes are the smallest units of sound that make a difference in meaning. Allophones are variants of the same phoneme.