Толковый словарь английского языка Oxford English Reference - bivalent

adj. & n. --adj. 1 Chem. having a valency of two. 2 Biol. (of homologous chromosomes) associated in pairs. --n. Biol. any pair of homologous chromosomes. Derivatives bivalency n. Etymology: BI- + valent- pres. part. stem formed as VALENCE(1) BIVALVE n. & adj. --n. any of a group of aquatic molluscs of the class Bivalvia, with laterally compressed bodies enclosed within two hinged shells, e.g. oysters, mussels, etc. --adj. 1 with a hinged double shell. 2 Biol. having two valves, e.g. of a pea-pod.