Despite previous efforts to unify the terminology for Cyperaceae, two different terms, perigynium and utricle, are in common use for the prophyllar bract enclosing the female flower of Carex. Use of these terms is divided largely on geographic lines (mainly North American versus European and other authors, respectively). The recent merging of Kobresia with Carex requires a single term to refer to both the open prophyll of Kobresia and the laterally closed one of Carex. However, even when authors use utricle for Carex species, these same authors do not refer to the open prophyll of Kobresia as a utricle. We show that perigynium was apparently coined earlier than utricle, at the end of the 18th century, but the term utricle became more widespread than perigynium by the 20th century. Neither of the two terms is unambiguous, as both have also been used for other structures in other plant groups. Given this background, we propose revised definitions of both terms based on two facts: 1) the greater semantic accuracy of perigynium to refer to both the prophylls of Carex and the former genus Kobresia; and 2) the greater spread, and thus social utility, of the term utricle. We also discuss the terminology used for the fertile prophylls of lower branching orders found in some Carex groups and recommend use of the terms cladoprophyll, tubular cladoprophyll, and utriculiform cladoprophyll.