In group theory, a field of mathematics, a double coset is a collection of group elements which are equivalent under the symmetries coming from two subgroups, generalizing the notion of a single coset.[1][2]
^Hall, Jr., Marshall (1959), The Theory of Groups, New York: Macmillan, pp. 14–15
^Bechtell, Homer (1971), The Theory of Groups, Addison-Wesley, p. 101