The article presents a description of the acquisition of verbal grammatical categories in a monolingual Czech-speaking boy. First the child produces only a limited number of forms, and the 3rd person singular present tense functions as a base form.
Then the 1st person singular and plural appear. In parallel, the child learns to use tenses - present tense prevails for imperfective verbs, future tense and past participles for perfective verbs.
The directive function is expressed by infinitives before the imperative is acquired. The conditional and passives are acquired at the end of the phase.
The author argues that the main principle of acquisition is the pragmatic principle.