Indefinites and the Type of Sets explores a new theory of indefinite noun phrase interpretation and definiteness effects. The book begins by introducing an adjectival theory of noun phrase interpretation and the relevant aspects of the semantics of noun phrases, and also providing comparisons with alternative theories. In the remainder of the book, Landman uses the adjectival theory of indefinites to develop a new account of various types of definiteness effects. Indefinites and the Type of Sets is written accessibly by one of the world's most prominent formal semanticists and is a valuable resource for students and scholars in formal semantics, as well as the neighboring fields of syntax, pragmatics, and the philosophy of language.