Lexicon is the study of the words and underlying concepts in the speaker’s mental dictionary.
Morphology is the study of internal word structure. Morphemes, the smallest meaningful units of language, combine to make words.
Phonetics is the study of speech sounds. Articulatory phonetics studies speech sound production; auditory phonetics deals with speech sound perception; acoustic phonetics focuses on physical properties of speech sounds.
Phonology is the study of the sound system. It examines the sound inventory of a language, sound patterns, and sound changes.
Pragmatics is the study of language in a social context.
Semantics is the study of the meaning of morphemes, words, phrases, and sentences.
Syntax is the study of the rules of sentence formation. Morphemes and words combine to make phrases and sentences.