The article explores the semantic classes of words conveying modal meanings and determines their place within the ideographic pattern of a dictionary. The author studies binary oppositions making up such classes of words as possibility-impossibility, obligation-optionality, etc. In the article, closer attention is paid to the commonness-exceptionality class, illustrating the combined and interpretational semantics of the words comprising the word-class in question, as well as relations of gradation between them.