perfect aspect

perfect aspect refers to an activity that has been finished or completed.

present perfect - I have washed the dishes.

1. activity has been completed and you can see the result
2. summing up how many times something has happened until now
3. summing up experience

present perfect continuous - I have been washing the dishes for five hours now and I'm exhausted.

1. to emphasize activity's duration
2. activity has been finished and you can see its immediate result
3. activity has been going on more often recently

past perfect - I had washed the dishes before I went to bed.

1. to talk about activity that happened before another activity in the past

past perfect continuous - I had been washing the dishes for 15 minutes before I realized there was no hot water.

1. to emphasize activity's duration
2. to emphasize some immediate results

future perfect - By the end of the day, I will have washed the dishes.

1. At some point in the future an action will have been completed

future perfect continuous - By the end of this song, I will have been washing the dishes for half an hour.

1. to emphasize activity's duration

perfect infinitive - have + verb's 3rd form

1. to refer to the past activity after modal verbs

You should have stayed at home.

It can't have been him at the party.

You needn't have done it.

having done/ having been

1. after you have done something/ after something has happened to you

Having finished my dinner, I washed the dishes.

Having been warned of the danger, I took extra precautions.