As a branch of linguistics, morphology deals with the structure of words. This simple definition requires a little explanation though, since words have several types of structure. It can be rephrased as follows. Morphology deals with the correlation of form and meaning within the word. An example should make this clearer.

Consider the set of words illustrated in (1) below.

Some related words in English

The word in Column 2 always indicates an adjective meaning ‘like or suitable for the person mentioned in Column 1’. So neighbourly means ‘like or suitable for a neighbour’ and so on. These meanings are associated with a constant difference in form: there is always an extra -ly (or we could formulate the same thing in terms of sounds) at the end of the word. The difference in meaning between the words in Columns 2 and 3 is likewise predictable on the basis of their form. The word in Column 3 always means ‘a characteristic of people who can be described by the word in Column 2’ (so that motherliness means ‘a characteristic of motherly people’). Again the difference in form is the same in all the Column 3 words, the addition of -ness and, in the spelling though not in the sounds, a change from y to i immediately before the -ness. These examples show a correlation between form (e.g. the addition of -ness) and meaning (e.g. the addition of the meaning ‘a characteristic of being like a person’). These are morphological relationships, the kind of patterns that morphology accounts for.