Introduction to Morphology

Morphology looks at the internal structures of words, or how words are made and how we make new words.

The smallest unit of meaning is called a morpheme (eg. un- or –er).

We can divide words into three broad categories 
1) Simple words (1 morpheme, eg. cat, paper) 
2) Complex words (<1 morpheme, eg. un+fortun(e)+ate+ly, print+er)
3) Compound words (a new word made of 2 existing words, eg. sketch+pad, bitter+sweet)

We would be unlikely to consider cat and cats as two different words. 
We can therefore call cat a lexeme. This is the abstract, representative form of a word. 

This is also useful for conceptualizing multi-word verbs / nouns. (eg. to put off).

Some lexemes have more than one meaning. This is called polysemy. 
mouse – a small rodent 
mouse – a piece of computer hardware.

We can also use the term ‘lexical item’. 
A lexical set refers to a group of closely related words. For example: apple, orange, bananas, pineapple, papaya are all names of fruit.