Defective verb

From Teflpedia

A defective verb (/dəfektɪv( v)ɜ:b/) is a verb with incomplete conjugation, or one which cannot be used in some other way as normal verbs can, i.e. defectivity. Defective verbs cannot be conjugated in certain tenses, aspects, or moods.[1]

In English modal verbs are defective because they do not have an infinitive, present participle, past participle or gerund.

There are sundry other defective verbs in English, particularly beware.

Impersonal verbs are in a sense semi-defective.