The main goal of this dissertation is to consider the different types of indefinites in Russian as a system and provide a semantic account for each of them that would be able to naturally explain their distribution. The four sets of so-called 'indefinite pronouns' ("-to," "-nibud'," "-libo," and "koe-" indefinites) differ in their degree of specificity. Indefinites with the prefix "koe-" are epistemically specific (known to the speaker, but unknown to the addressee). They also induce the effect of proportionality (and refer to a part of a given set). As such, they can be analyzed as unambiguously choice-functional proportional indefinites. Indefinites with the suffix "-to" are usually analyzed as scopally (but not epistemically) specific. The conclusion that they can only take a wide scope often leads to analyzing them as choice-functional items as well. Such an approach, though, requires some additional stipulations to be made to distinguish "-to" and "koe-" indefinites. It also fails to account for the cases when "-to" indefinites are perceived as having a narrow apparent scope. I propose that "-to" indefinites are instances of the parameterized choice function with an implicit argument which can be bound from outside; in particular, the function can be parameterized by times yielding the quazi-narrow-scope interpretation. Under such an analysis, "-to" indefinites are not classic choice-functional indefinites because they can behave similar to quantifiers when the implicit parameter is bound from outside. Traditional approaches to "-nibud'" indefinites are based on their non-specificity or/and peculiar distribution (they are only licensed in questions, conditional sentences, imperatives, future tense sentences, in the scope of modal operators, and in some characterizing/generic sentences, e.g. dictionary definitions). I propose that their syntactic distribution is due to their domain-widening semantics. The indefinites with the suffix "-libo" are very similar to "-nibud'" pronouns in their semantics and functions. The only difference lies in the degree of universality. "-Nibud'" indefinites can never receive a universal interpretation, "-libo" items, however, seem to function as universals in comparisons and under negation. This difference is caused by another, stylistic in nature, property of the system: only a formal-style "-libo" but not a stylistically neutral "-nibud'" is able to function as a universal (free choice) indefinite in some contexts, because the truly free-choice items do not meet the stylistic requirements of these contexts. The system of the different sets of Russian indefinite pronouns, then, covers the whole continuum of "indefiniteness" via non-overlapping in their semantics and functions lexical items: from mere choice-functional "koe-" items through "half-quantificational" "-to" indefinites to domain-widening (quantificational) "-nibud'" indefinite pronouns. The indefinites demonstrate competition and distribution of labor. Each of the indefinites has its own semantics and functions, but at the same time their semantics and behavior are closely tied to and dependent on the other parts of the system. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]