The present study deals with suffixless nouns in Czech. Two data samples are analysed to demonstrate that suffixless nouns with an action meaning mostly correspond to a pair of verbs with different themes (conveying different grammatical aspects; e.g., skok ‘jump’ < skočit ‘to jump. PFV’ : skákat ‘to jump.IPFV’), whereas non-actional suffixless nouns tend to form a single corresponding verb which uses a prefix to change the aspect (noc ‘night’ > nocovat ‘to stay.IPFV overnight’ > přenocovat ‘to stay.PFV overnight’). This distinction is applied to a third data sample to determine direction of motivation in pairs of suffixless nouns and verbs. The difference between the deverbal and denominal direction is explained by the part-of-speech category of the root morpheme which is shared by the suffixless noun and the corresponding verb(s). The relations observed are modelled as paradigms recurring across the word-formation system of Czech.