ROGET THESAURUS
Duality
VB
pair, couple, bracket, yoke,
conduplicate, mate, span.
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.