The article deals with the problem of language categorization on the sentence level. A cognitive approach to the sentence study reveals polysemy of a sentence generally depends on the sentence possibility to categorize different variations of a prototypical situation. These variations stand on two basic factors. Firstly, great numbers of alike but not equivalent situations exist in real life. A person, since he / she is capable of categorizing, confines a situation to a certain category. Secondly, the speaker can differently interpret the same situation. The latter may focus attention on different dimensions of the situation at different time. As a result, some dimensions of the situation are highlighted and the others, on the contrary, recede to the background. Nonequivalence of the similar situations and different interpretation of the same situation determine semantic and syntactical structure of the sentence. The prototypical situation of speech has been chosen for analysis to manifest this statement.