The book considers the linguistic criterion for determining homonymy and for differentiating it from the ambiguity of a word. As such a criterion, an exhaustive consideration of the rules of syntactic and lexical compatibility of a word is proposed. The analysis of the possibility and probability of certain combinations, carried out on a fairly wide material of the Russian and German languages, allows us to show the difference between polysemia and the decomposition of a word into two or more lexemes.