ROGET THESAURUS
twins
Duality
N
duality, dualism, duplicity, biplicity, biformity, polarity, two, deuce, couple, duet, brace, pair, cheeks,
twins, Castor and Pollux, gemini, Siamese
twins, fellows, yoke, conjugation, dispermy, doublets, dyad, span, two, twin, dual, dualistic, double, binary, binomial, twin, biparous, dyadic, conduplicate, duplex, biduous, binate, diphyletic, dispermic, unijugate, tete-a-tete, coupled, conjugate, both, both the one and the other.