Main Entry: di·chot·o·my

Etymology: Greek dichotomia, from dichotomos Date: 1610

1: a division into two especially mutually exclusive or contradictory groups or entities; also : the process or practice of making such a division

2: the phase of the moon or an inferior planet in which half its disk appears illuminated

3 a: bifurcation; (as of a plant's stem)
b: a system of branching in which the main axis forks repeatedly into two branches
c: branching of an ancestral line into two equal diverging branches

4: something with seemingly contradictory qualities