Syntax
The study of the grammatical form of sentences: what makes the sentence "he gave the book to Mary" have the form of a typical English sentence, while the sentence "gave he book the Mary to" does not?
Semantics
The study of the meaning of sentences: in the sentence "he gave the book to Mary" what was happening? who was doing the giving? who was doing the receiving
Pragmatics
The study of how sentences are used to communicate: what are the rules of discourse that mean we can follow each other's conversations; why when someone asks you "Can you tell me the time?" you don't answer "yes" or "no".
Morphology
The study of the form of words: how groups of words share related meanings through regular patterning: what links "like", "likes", "liked", "likeness", "likely", "likelihood"?
Phonology
The study of the pronunciation of words and sentences: what basic sounds are used by a language, what regular patterning occurs in words; why does the sound used at the end of the word "sing" not occur at the beginning of a word?
Phonetics
The study of the production of speech by the human vocal mechanisms: how are sounds made, how do speakers of different accents differ..
Psycholinguistics
The study of the mental processes by which sentences are constructed and decoded by human beings.
Sociolinguistics
The study of how language variation is related to its use in society to form groups of geographical region, economic class or ethnicity.
Computational linguistics
The study of how computers can be used to analyse and generate sentences.