Monolingual dictionaries are by their very nature truly defining, unlike bilingual ( ormultilingual) dictionaries, translation dictionaries. This article is mainly about thesemantic basis of definition.Having distinguished in the lexicon of a natura! language lexical elements representing"languages within the language", that is, words which are provincial, sociallyand stylistically marked, as well as purely technical terminology, the author discussesthe more uniform system of a standard language. The key concept is lexeme. Alexeme can correspond to a word in the traditional sense but can also correspond to adistinct use of a word. lgnoring the phenomenon of synonymy, a lexeme contrastswith every other lexeme. There are also elements of oppo...