摘要：The theoretical part of this article is focused on verbal aspect,particularly on biaspectual verbs in Czech. The creation of a perfective verb from a biaspectual verb by means of prefixation is described. Within corpus research,usage of biaspectual verbs in a perfective context is explored in contrast to its perfective correlate. Then we focus on syntactic restrictions,considering the usage of certain biaspectual verbs,and on the fact that the aspect of biaspectual verbs cannot be identified out of context. Czech biaspectual verbs develop over time and they can also lose their biaspectuality over time. The perfective forms of biaspectual verbs were verified for the following verbs: adaptovat,definovat,organizovat,faulovat,kontaktovat,realizovat,exportovat,publikovat,kompromitovat and korumpovat. Our research indicates that half of the selected verbs cannot be used in their perfective forms in time-subordinate sentences,and that in this type of sentence they are replaced by their prefixed perfective correlates. This finding leads us to the conclusion that in certain contexts,Czech biaspectual verbs can lose their biaspectuality over time.
