ABSTRACT
The modal auxiliaries comprise nine words: can, could, may, might, shall, should, will, would and must. They are sometimes called modal verbs, but here they are treated as a separate word class, distinct from verbs, because: unlike verbs, they constitute a closed word class; their grammar is very different from that of verbs; and the meanings they refer to are to do with the idea of modality. They are sometimes called 'defective' verbs because they have: no infinitive form, no third-person -s present tense, no past tense and no -ed or -ing participles. Structurally they form the first part of verb phrases. There are many, sometimes overlapping, and meanings. In the most general terms they all have the idea of modality: drawing back from a factual statement to limit the meaning of verbs, similar to the way determiners affect nouns. This involves them in pragmatic factors such as tentativity, commitment, politeness and formality.
