Perfect

Perfect is an English aspect. This aspect uses auxiliary have and the past participle. The four perfect aspect forms are as follows:

1. The Present perfect: I have worked here for over twenty years. - You have gone
2. The Present perfect progressive (or present perfect continuous): He has been working. - They have been living.
3. The Past perfect: We had worked it all out. - I had spoken to him on several occasions.
4. The Past perfect progressive (or past perfect continuous): I had been working all morning on that. - He had been living there until he got that new place.

Some writers call #1 the Present Perfect Simple and #3 the Past Perfect Simple, but most prefer to use the word 'Simple' only for tenses that are both non-progressive and non-perfect, i.e. the Present Simple and Past Simple.

The perfect tenses in English are used to relate two time points or periods: 1. the time at which the situation denoted occurred or began, and 2. a later time point or period. It has been suggested that 'Retrospective' would be a more appropriate name for these forms.