This paper documents and analyzes the pattern used in the Northwest Caucasian language Adyghe (Circassian) to express what the following five different constructions convey in other languages: headed and headless relative clauses, embedded declaratives, embedded polar interrogatives, and embedded constituent interrogatives. We argue that Adyghe encodes the meanings of all these embedded structures by means of the same syntactic construction, a relative clause. This pervasive use of relative clauses is possible due to mechanisms that are independently attested not just in Adyghe but also in more familiar languages like English. These mechanisms include concealed questions, polarity operators, and nominals such as fact and question that can connect propositional attitude verbs or interrogative verbs with embedded clauses. We suggest that this extensive use of relative clauses in Adyghe is triggered by the absence of non-relative complementizer. We further show that this use is facilWe are very grateful to our language consultants Raxmet Eshev, Raxmet Gishev, Svetlana Kinokova, and Mira Unarokova for their help with the language data. This paper owes its initial inspiration to the pioneering findings by Yury Lander and Yakov Testelets, who have been very generous in discussing their findings with us. We are particularly indebted to Peter Arkadiev and Brian O'Herin for their very detailed comments on this work. We would also like to thank Ayla Appelbaum, Daniel Büring, Gennaro Chierchia, Marcel den Dikken, Shin Fukuda, Anastasia Giannakidou, Matt Gordon, Daniel B. Kane, Richard Kayne, Ed Keenan, Christopher Kennedy, Min-Joo Kim, Shin-Sook Kim, Alexander Letuchiy, Eric Potsdam, Greg Scontras, Kirill Shklovsky, Donca Steriade, Virginia Yip, and three anonymous reviewers for helpful suggestions. Parts of this work were presented at SALT 18, WCCFL 27, GLOW 31, CUNY Graduate Center, Zentrum für allgemeine Sprachwissenschaft in Berlin, the University of Chicago, and Yale University. We are solely responsible for all the errors in this paper.I. Caponigro ( ) Department of Linguistics, University of California San Diego, 9500 Gilman Drive, 0108, La Jolla, CA 92093-0108, USA e-mail: ivano@ucsd.edu M. Polinsky Department of Linguistics, Harvard University, Cambridge, MA 02138, USA e-mail: polinsky@fas.harvard.edu 72 I. Caponigro, M. Polinsky itated by their morphological visibility: a relativizer realized as a prefix on the verb, verbal affixation, a rich system of applicative heads hosting indirect arguments, and the availability of a case marker suffixed to headless relatives. We conclude by discussing the implications of the Adyghe system for the general design of embedding and subordination in natural language.