EN
Different functioning of verb pairs of the type wpuścić-wpuszczać from the type kwiść-zakwiść proves that aspect oppositions were developed originally according to the following word-formation patterns a perfective verb form - an imperfective verb form derived by suffixation. In Old Polish the stem of the perfective form in a verb pair usually ended with -i. Further development of aspect oppositions results from the interaction of verb pairs which either are or are not ал aspect pair. Consequently, there is a considerable effect of current word-formation tendencies on aspect oppositions or quite the opposite: word-formation mechanisms may be modified as the result of functioning of aspect oppositions.