Why is 'present perfect' present if it happened in the past? And why is it 'perfect'?
Present Perfect is called like that because it combines the present grammatical tense (you have) and the perfect grammatical aspect (done). Compare that to Past Perfect which uses the past tense (you had + done), or the Future Perfect which uses the future "tense" (you will have + done). The term perfect comes from Latin perfectus, "achieved, finished, completed".
The present perfect, like the simple past, locates the situation, or part of it, in the past:
However, the present perfect is a compound tense that combines the present and the past, while the simple past is purely a past tense.
Here are some reasons its called the present perfect, and not just the past tense:
Use of time adjuncts
The present perfect allows the use of time adjuncts referring to the present.
Conversely, the present perfect does not allow the use of time adjuncts referring to the past.
With the present perfect, the situation in the past is seen to have some kind of current relevance. Compare these two:
Use of the present perfect in the first sentence indicates that she still lives in this city while use of the simple past in the second indicates that she lived in this city in the past, but no longer does.
I've quoted quite a bit from the very descriptive A Student's Introduction to English Grammar by Huddleston and Pullum.
As noted in @RegDwight's answer, I understand that the perfect part comes from the Latin perfectus, meaning "completed".
protected by RegDwigнt♦ May 5 '12 at 18:50
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