Standard English has a closed class of central modal verbs (can, may, must, etc.) with highly specific properties. These modal verbs trigger the use of the bare infinitive, shun the otherwise obligatory third person -s suffix, possess no past tense forms, never occur together, do not trigger do-periphrasis – to mention just a few salient properties. In addition to the class of central modals, there are various so-called ‘semi-modals’ (dare, need, ought to, used to, have to, be able to, etc.) that have properties of both modal verbs and main verbs.

In this chapter, we will first of all familiarise ourselves with the special grammatical properties of the standard English modal verb system before considering their form, function, and distribution in non-standard varieties. In our cross-linguistic section, we will explore a broader array of strategies to encode modal meanings and also follow up the developmental paths of modal verbs, as the grammatical processes forming them are of wider significance.

Overview

In the standard varieties, the modal verbs can, could, will, would, may, might, must, shall, and should form a so-called ‘closed class’, as this group developed in the history of English – in the period known as ‘Early Modern English’ – and has remained largely unaltered since.

Modal verbs represent a subgroup of the wider category of auxiliary verbs with which they share many properties. Prototypical auxiliaries in English are be, have, and do, though these verbs may also be used as main verbs. ‘Auxiliary’ is the established term for a verb that assumes a function similar to that of verbal inflection (i.e. tense, mood, aspect, voice, etc.) and that does not form a predication of its own.