For the first time in linguistics, the article distinguishes negative pronouns of a pronoun-noun and pronoun-adjective. Their lexical meanings, grammatical features and syntactic functions are determined. A negative pronoun is a noun that means ‘nothing’ (in Russian both - ничто and ничего ), a negative Russian pronoun что meaning ‘whatever, none’. Both pronouns function as the principle sentence component, mainly in negative genitive sentences or as a predicate in a two-memberSubject-Predicate sentence. Subject of a pronoun-noun, which is expressed by the noun of any lexico-grammatical category or infinitive, with a negative pronoun-adjective, which is an infinitive. Both negative pronouns function in rhetorical questions expressing negation in the affirmative form. Subject combined with a pronoun-noun could be expressed by a noun of any lexico-grammatical category or infinitive, with a negative pronoun-adjective что , which could also be formed by an infinitive. Both negative pronouns function in rhetorical questions expressing negation in the affirmative form. The meanings of both negative pronouns are syntactically limited (by the function of the predicate or the principle component of the negative genitive sentence) and structurally determined (be found in the construction with the dative of the authorizer). The meaning of a negative pronoun-adjective is also phraseologically confined, a negative pronoun is an adjective that is always used with the Russian words like проку, толку, выгоды, пользы, прибыли, добра . Three meanings stand out for a negative pronoun ничто : 1) ontological vacuum, nonexistence, absence of an object; 2) something insignificant, insignificant, not worthy of attention; 3) denial of the significance of a person, insignificance. A negative pronoun что is a noun that means ‘something insignificant, insignificant, not worthy of attention’ (or ‘(as it were) the absence of something/someone (for the authorizer)’), or ‘absence (of benefit)’. A negative pronoun что is an adjective that has one of the meanings of a negative pronoun-adjective никакой meaning ‘none of the available or possible’. Despite the indeclinability, a negative pronoun что expresses the noun-meanings of the nominative and genitive cases, while being a negative pronoun-adjective to denote the genitive case, either masculine or feminine. The data collected is retrieved from the National Corps of the Russian Language (NCRL). As the main methodological technique, the substitution method was applied. The theoretical basis of the article was the work on homocomplexes, functional homonyms, poly-functional words, the differentiation of homonymy and polysemy. The theoretical significance of the study lies in the fact that the results allow us expand the linguistic understanding of the semantic and grammatical nature of the pronoun as well as the issue of pronoun syncretism in general, the differentiation of homonymy and polysemy of the classes of pronouns, as well as the varieties of genitive sentences. The data collected can be useful for lexicographic practice: compiling dictionaries of homonyms, grammatical homonyms, explanatory dictionaries, as well as to clarify the typology of one-member sentences. The relevance of the topic is determined by the necessity to establish the full list of pronouns in the Russian language, as well as the importance of studying the phenomena of functional homonymy, transition and syncretism and the importance of solving the problem of distinguishing homonymy and polysemy.