The paper considers the problem of choice between the construction U Y-a est´ Х lit. ‘At Y is X’ (with the form est´ of the verb BYT´ ‘be’) and the construction U Y-a Х lit. ‘At Y X’ (with the zero form of the verb BYT´). This choice is determined by the meaning to be expressed, that is, practically it can be reduced to the choice of the corresponding one of several verbs BYT´ ‘be’. As the first approximation, the starting meaning ‘Y is a semantic actant of X’ (U IvanaY temperaturaХ / èkzamenХ / dvoe detejХ ‘At Ivan [high] temperature / [an] exam / two kids’) is expressed by the verb BYT´II.3 and by the construction U Y-a Х; the meaning ‘Y has Х’ (U IvanaY est´ dačaХ / special´nyj pomoščnikХ / vremjaХ ‘At Ivan is [a] summer.house / [a] special assistant / time’) is expressed by the verb BYT´III.2 and by the construction U Y-a est´ Х. The paper also presents the vocable BYT´, with 13 lexemes; five of these, which participate in the constructions under analysis, are accompanied with full lexicographic descriptions. A series of particular cases is analyzed in which the choice of the appropriate construction is complicated by additional conditions. Formal semantic rules for the production of both constructions are supplied.