The perfect aspect is an aspect of verbs that are present in many languages. By this aspect it is expressed that the said act as such is entirely in the past, that is, it is complete, or that the act is regarded as a completed whole. This is often referred to as just a single moment in the past, as is the case with the Greek aorist, the French passes simple and the English simple. The perfect aspect is used in, among other things, Russian to also indicate a purpose or result; In this case, the action does not have to have an explicit temporal component, because it may also be in the future.
The perfect aspect differs from the imperfect aspect temporarily; In Slavic languages this distinction is also morphological: verbs of both aspects have different forms and are thus identifiable as imperfect or perfect.
The imperfect aspect sees the action from within: it is the act itself that is current, not its demarcation in time. In the imperfect aspect of the past, an act is described which belongs to the past, but the emphasis is more on its continuing nature and thus its not yet complete. In French, this distinction is obviously present in the distinction between the imperfective imparfait and the perfect passé composé.
However, there are a number of instances where the boundary between imperfect and perfect can be less sharp, for example:
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