How is it formed?
Affirmative
I've
He-She-It 'sworked yesterday
You-We-They 've

Negative
Ihaven't
He-She-Ithasn'twoked all day
You-We-Theyhaven't

Interrogative
HaveI
HasHe-She-Itworked yesterday
HaveYou-We-They

Affirmative Short answers
YesIhave
YesHe-She-Ithas
YesYou-We-Theyhave

Negative Short answers
NoIhaven't
NoHe-She-Ithasn't
NoYou-We-Theyhaven't

To form the Past Simple we add ed to the base form of all regular verbs. For spelling and pronunciation see boxes below. For irregular verbs which have their own form of the Past Simple look at the table at the end of Unit…. pag... The interrogative and negative is formed with did/didn’t + base form for both regular and irregular verbs.

It can be used for advice:
e.g.
Drive carefully! [Guidi/guidate con cura!]