The Russian verb has 3 tenses and 2 aspects. Aspects describe different qualities of an action—it is either acting (the process of doing something—Imperfective) or the result of an action (after someone has finished doing something—Perfective). Using the Imperfective/Perfective depends only on the intention of the speaker to emphasize different aspects of action in his or her speech.
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Table of difference between two aspects
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The Perfective aspect of Russian verbs is formed from the Imperfective by using different prefixes and suffixes.
[table “” not found /]Aspects of verbs denote tenses
The Perfective can be used only in the Past or Future Tense, since the result can be reached only in past, and there is still a chance that there will be a result in future. Also please note that verbs in the Perfective aspect in the Future Tense change persons as verbs in the Imperfective aspect in the Present Tense.
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Original Here: http://learnrussian.rt.com/grammar-tables/aspects-of-russian-verbs–imperfective-and-perfective/