Although the formation and uses of aspects in different Slavic languages has a great deal of similarity, I have detected cases in which an imperfective in Russian does not necessarily mean an imperfective in Czech or Polish or a perfective in Russian would not be the case in Czech and Polish. I'll give a few examples based on what I have observed. Please correct me in case I am mistaken. The imperfective in negative past statements in Russian means that the speaker had no intention to perform the action expressed by the main verb: Russian: Студенты не писали эти упражнения. (The students didn't do these exercises [and didn't plan to do them].) Polish: Studenci nie zrobili tych zadań. Czech: Studenti neudělali ta cvičení. In Russian, when a question is asked with the imperfect, the questioner is not concerned about the result of an action, but simply wants to know whether an action took place: Russian: Дети писали письмо? Polish: Czy dzieci napisały list? Сzech: Napsaly děti dopis?