Abstract
The present study attempts to comprehensively describe rules determining the choice of long or short vowel in verbal nouns. The author focuses on the vowels a and á in verbal nouns ending in -ání or -aní that are not systematically described from a synchronous point of view.
The distribution of these deverbatives is also confusing to learners. As a result, they are not able to differentiate between the two endings if they are not given any clear rules.
Therefore, this analysis focuses on identifying the rules in use of analysed endings in the Czech language based on data of contemporary written Czech in the SYN2015 corpus, with regard to learners of Czech as a foreign language. The data has shown that the choice between the endings -ání or -aní is necessary only in the case of two-syllable verbal nouns; multi-syllable verbal nouns always end in -ání.
The correct ending of a two-syllable noun can be identified based on the infinitive of base verb. If the vowel is shortened in a prefixed infinitive (ex. psát - napsat) then the two-syllable noun has the ending -aní (ex. psaní).
If there is no shortening (ex. tát - roztát), a two-syllable noun ends in -ání (ex. tání). The rules formulated in this way systematize the hitherto confusing distribution of the endings -ání and -aní that can be considered as regular with regard to the most frequent verbal nouns.
This knowledge can be further applied in teaching of foreigners regarding creation of new teaching materials.