Knowledge of morphology is knowing the underlying form of a word and the derivations that can be made from it. For example, the English word 'dissatisfaction' is made up of a prefix denoting opposite ('dis'), a common noun suffix ('ion'), and is derived from the root word 'satisfy'. In our teaching, we should not be shy of pointing out relationships between parts of speech having a common root, since this type of knowledge facilitates understanding, especially for language learners whose own language is rich in such networks. There is evidence from second language acquisition studies (eg Nagy et al, 1989) that the members of a word family are grouped together in the mind.