Phonology is the study of how sounds are organized and used in languages. It examines an inventory of sounds and rules for how they interact, and analyzes sound patterns to determine which sounds are significant for a language. Phonetics studies speech sound production, while phonology analyzes sound patterns and interpretations in a particular language. A phoneme is the smallest meaningful sound unit that distinguishes word meanings. Generative phonology assigns phonetic representations to utterances based on a speaker's internal grammar. Non-linear models like autosegmental and metrical phonology treat representations as multi-dimensional. Lexical phonology accounts for interactions of morphology and phonology in word formation through ordered levels.