Synonyms and related words :
ambidextrous, bifacial, bifold, biform, bilateral, binary, binate, biparous, bivalent, conduplicate, disomatous, double, double-faced, dual, duple, duplex, duplicate, geminate, geminated, second, secondary, twin, twinned, two-faced, two-level, two-ply, two-sided, two-story, twofold