1) Phonetics, Phonology This is the level of sounds. One must distinguish here between the set of possible human sounds, which constitutes the area of phonetics proper, and the set of system sounds used in a given human language, which constitutes the area of phonology. Phonology is concerned with classifying the sounds of language and with saying how the subset used in a particular language is utilised, for instance what distinctions in meaning can be made on the basis of what sounds.
2) Morphology This is the level of words and endings, to put it in simplified terms. It is what one normally understands by grammar (along with syntax). The term morphology refers to the analysis of minimal forms in language which are, however, themselves comprised of sounds and which are used to construct words which have either a grammatical or a lexical function.
Lexicology is concerned with the study of the lexicon from a formal point of view and is thus closely linked to (derivational) morphology.
3) Syntax This is the level of sentences. It is concerned with the meanings of words in combination with each other to form phrases or sentences. In particular, it involves differences in meaning arrived at by changes in word order, the addition or subtraction of words from sentences or changes in the form of sentences. It furthermore deals with the relatedness of different sentence types and with the analysis of ambiguous sentences.
Language typology attempts to classify languages according to high-order principles of morphology and syntax and to make sets of generalisations across different languages irrespective of their genetic affiliations, i.e. of what language family they belong to.
4) Semantics This is the area of meaning. It might be thought that semantics is covered by the areas of morphology and syntax, but it is quickly seen that this level needs to be studied on its own to have a proper perspective on meaning in language. Here one touches, however, on practically every other level of language as well as there exists lexical, grammatical, sentence and utterance meaning.
5) Pragmatics The concern here is with the use of language in specific situations. The meaning of sentences need not be the same in an abstract form and in practical use. In the latter case one speaks of utterance meaning. The area of pragmatics relies strongly for its analyses on the notion of speech act which is concerned with the actual performance of language. This involves the notion of proposition – roughly the content of a sentence – and the intent and effect of an utterance.