Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

MODAL FORMS

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The most significant expression of modality is by means of modal verbs. The core

modal verbs are: can, could, may, might, will, shall, would, should, must.

There is also a set of semi-modal verbs. These verbs behave in similar ways 

to core modal verbs but share some characteristics with lexical verbs. The 

semi-modal verbs are: dare, need, ought to, used to.

This chapter also describes other expressions of modality apart from the modal

and semi-modal verbs. For example we consider the role of other verbs which can

express modal meanings (e.g. hope, manage, suppose, seem, wish, want) and

modal phrases which have become grammaticalised (e.g. had better, be meant to,

be obliged to

, be supposed to). The chapter also refers to expressions of modality

by means of adjectives, adverbs and nouns.