Page "Morphology (linguistics)" Paragraph 30

Given the notion of a lexeme, it is possible to distinguish two kinds of morphological rules.

Some morphological rules relate to different forms of the same lexeme ; while other rules relate to different lexemes.

Rules of the first kind are called inflectional rules, while those of the second kind are called word formation.

The English plural, as illustrated by dog and dogs, is an inflectional rule ; compound phrases and words like dog catcher or dishwasher provide an example of a word formation rule.

Informally, word formation rules form " new words " ( that is, new lexemes ), while inflection rules yield variant forms of the " same " word ( lexeme ).