The principal parts (/prɪnsɪpəl pɑ:ts/) of a verb are those four forms from which all other forms may be constructed. For example, the principal parts of eat are eat, ate, eaten, eating. Some verbs are defective verbs and do not have all of these forms available for use. For regular verbs these are regular (albeit sometimes with minor spelling changes), but irregular lexical verbs are, well, irregular.
|eat, play||Used, without change, as the bare infinitive, first and second persons singular of the Present Simple tense. With the addition of third person -s with certain other changes with some verbs (see Present Simple: Form), it is used for the third person singular for of that tense.|
|ate, played||Used for the past simple tense. For regular verbs it is identical to the past participle.|
||eaten, played||Used for the perfect aspect and the passive voice. For regular verbs it is identical to the preterite.|
|eating, playing||Used for the progressive aspect.|