Real Dictionary

principal parts in American English
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 pre
plural noun: a set of inflected forms of a form class from which all the other inflected forms can be derived, as sing, sang, sung; smoke, smoked

principal parts in British English
plural noun: the main inflected forms of a verb, from which all other inflections may be deduced. In English they are generally considered to consist of the third person present singular, present participle, past tense, and past participle