Phonetics and Phonology.
Phonetics and phonology is the study of sounds and sound patterns. This explores spoken language, in particular how sounds are used, how they are formed into patterns, how they change depending on circumstances and how pitch, stress and intonation can effect meaning.
Morphology and Lexicology.
Morphology is concerned with the study of the structure and formation of words, as well as classifying them into different parts of speech and how they vary in form for grammatical reasons. While lexicology explores what a word is, how the meaning of words can be explained, the etymology of words, their meanings and how these words relate to each other.
Syntax.
Syntax refers to the study of phrases, clauses and sentences. It recognises how words are joined together to make phrases and clauses, which are joined together to make sentences.
Discourse Analysis.
Discourse analysis is the study of connected sentences and how the connect to form texts. The organisation and structure of sentences and groups and how the arrangement of our messages provide information and cues for interpretation.
Semantics.
Semantics explores the meaning of words, and how this meaning is made through the features outlined in the other subsystems.