Janus, ambiguity, ambivalence, bifidity, biformity, bifurcation, bipartition, bisection, branching, by two, conjugation, cutting in two, dichotomy, dimidiation, division, doubleness, doublethink, doubling, dualism, duality, duplexity, duplication, duplicity, equivocality, forking, in half, irony, pairing, polarity, ramification, subdivision, twinning, two-facedness, twoness