Principal parts

The principal parts of the irregular Lexical verb are those three forms from which all other forms may be constructed. For example, the principal parts of GO are go, went, gone.

go is an example of the first form or base form. By itself it is used as the Bare infinitive, the Imperative and the first and second persons singular of the Present Simple tense. With the addition of -s, with certain other changes with some verbs (see Present Simple: Form), it is used for the third person singular for of that tense. With the addition of -ing, it is used for the Present participle, Gerund, and in the construction of Progressive aspects (see (Present Progressive: Form). With the addition of -d, with certain other changes with some verbs (see Past Simple: Form), it forms the Past Simple of regular verbs.

went is an example of the Second form. It is used for the Past Simple tense.

gone is an example of the third form, traditionally known as the Past participle. It is used in the construction of the Perfect aspect and the Passive voice.