Principal Parts Definition

noun

In traditional grammars of inflected languages, the forms of the verb that are considered basic and from which all other forms of the verb are derived.

American Heritage

The principal inflected forms of a verb, from which the other forms may be derived: in English, the principal parts are the infinitive, past tense, and past participle (Ex: drink, drank, drunk; go, went, gone): the present participle, derived from the present infinitive with the addition of -ing, is sometimes regarded as one of the principal parts.

Webster's New World

In English, the present infinitive ( play, eat, put ), the past tense ( played, ate, put ), the present participle ( playing, eating, putting ), and the past participle ( played, eaten, put ).

American Heritage