A 'word form is a form that can be derived from a lemma.
Sometimes words lack forms; these are linguistically defective.
In English, the following types of words have multiple forms:
- Nouns have up to two forms; a singular and a plural, but may be singular-only or plural-only.
- Verbs have up to 6 forms; a base form, to-infinitive, third person form, -ing form, preterite and past participle. With regular verbs, and some irregular lexical verbs, the preterite and past participle are identical in form.
- Adjectives and adverbs have up to three forms; a simple form, and two gradative forms; a comparative and superlative.