The past forms of the irregular verbs must be learnt by heart. Use the simple past (the second form of the verb) to talk about past events, e.g. buy – bought – bought:

Melissa bought a comic book for her niece.

The present perfect is formed with the present tense of the verb have and the past participle of the main verb (the third form), e.g.: know – knew – known:

I have known about their affair for months.

The past perfect is formed with the past tense of the verb have (had) and the past participle of the main verb (the third form), e.g.: know – knew – known:

I had known about their affair for months.

Irregular verbs: