One of the things I can across quickly while learning 55 common Polish verbs is the concept of aspect in Slavic languages. I found an excellent explanation on Wikipedia with, luckily for Polish learners, explanations of what perfect vs imperfect aspect is all about using examples using Polish verbs.
From Website
Imperfective verbs mean:
- actions in progress, just ongoing states and activities, with significant course (in opinion of the speaker);
- activities posing the background for other (perfective) activities, ex. czytałem książkę, gdy zadzwonił telefon 'I was reading the book when the telephone rang';
- simultaneous activities, ex. będę czytać książkę, podczas gdy brat będzie pisać list 'I will be reading the book while brother will be writing the letter';
- durative activities, lasting through some time, e.g. krzyczał 'he was shouting', będzie drgać 'it will be vibrating';
- motions without a strict aim, ex. chodzę 'I am walking here and there';
- multiple (iterative) activities, ex. dopisywać 'to insert many times to the text', będziemy wychodziły 'we will go out (many times)';
- non-resultative activities, only heading towards some purpose: będę pisał list 'I will be writing the letter';
- continuous states, ex. będę stać 'I will be standing'.
Perfective verbs mean past or future, but not present activities – an activity which is happening now cannot be ended, so it cannot be perfective. Perfective verbs mean:
- states and activities which were ended (even if a second ago) or which will be ended, with insignificant course, short or treated as a whole by the speaker, ex. krzyknął 'he shouted', drgnie 'it will stir';
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single-time activities, ex. dopisać 'to insert to the text', wyszedł 'he has gone out';
actions whose goals have already been achieved, even if with difficulty, ex. przeczytałem 'I have read', doczytała się 'she finished reading and found what she had sought';
reasons for the state, ex. pokochała 'she came to love', zrozumiesz 'you (sg.) will understand', poznamy 'we will get to know'; - the beginning of the activity or the state, ex. wstanę 'I will stand up' (and I will stand), zaczerwienił się 'he reddened';
- the end of the activity or the state, ex. dośpiewaj 'sing until the end';
- activities executed in many places, on many objects or by many subjects at the same time, ex. powynosił 'he carried out (many things)', popękają 'they will break out in many places', poucinać 'to cut off many items';
- actions or states which last some time, ex. postoję 'I will stand for a little time', pobył 'he was (there) for some time'.
