Defective verb
A defective verb is a verb with an incomplete conjugation. Defective verbs cannot be conjugated in certain tenses or moods.
Examples
- in English: can; ought (there is no infinitive "to can," for example)
- in French: pouvoir; gésir (there is no imperative "peux" or "puisse," for example)
- in Spanish: abolir (this is disputed, but some contend that there is no "él abole," for example)
Defective verbs in English
In the English language, there are few defective verbs. The only strictly defective verbs are "ought" and the modal auxiliary verbs, including:
- can/could
- may/might
- shall/should
- will/would
- must
- need (e.g. "it need not happen today" - though need is only marginally an auxiliary in that it functions as a full verb too: "it does not need to happen today")
These verbs lack several forms. Most notably, despite all having present indicatives, they do not have infinitives ("to can", "to shall"), participles ("am canning ", "am shalling"), imperatives, or subjunctives. Additionally, they make no distinction between the third-person singular and the other forms of the present tense ("he can" not "he cans"; "he ought" not "he oughts") though there are archaic second-person singular forms (such as "thou canst", "thou wilt").
