The article is devoted to the actual problem of forming students' communicative competence. It is noted that linguistic competence is a component of communicative competence, and lexical competence is a component of linguistic competence and consists in the ability to use vocabulary to express one's own opinion depending on the conditions of communication. The most frequent mistakes that occur in the speech of students of general secondary education institutions are noted: incorrect or inaccurate word usage; tautology; inability to use synonyms and phraseology; mixing words of different meanings but similar in sound (paronyms); words unnecessary in speech, meaningless words (parasitic words); unjustified calquing of Russian words and stable phrases (literal translation of them into Ukrainian); mixing Ukrainian and Russian words; use of redundant words, etc. The reasons for these mistakes are listed, among which the author identifies the following: non-normative speech influences; ignorance of the norm; inability or unwillingness to use dictionaries; impoverished vocabulary of students; stylistic conditionality of word use; hasty word choice and lack of self-control; underdeveloped language sense, etc. It is emphasized that among the methods of working on lexical errors, exercises take the leading place. Vocabulary exercises are used to enrich students' vocabulary, to develop their linguistic sense, and to test their knowledge of lexicology and phraseology. The didactic material presented in the article helps to solve practical problems. As a rule, these are cards with various tasks. The work with flash cards is of great interest. By completing tasks on them, students enrich their vocabulary, activate their mental activity, and develop self-control skills. Such work teaches students to find the information they need on their own, to work with reference books, and to develop information and communication competence.