Definition of: dichotomy

(dī·kot′ə·mē) noun plural ·mies
1. The state of being divided in two; division into two parts or into two branches; division by pairs.
2. Logic The division of a class into two mutually exclusive subclasses, one positive and the other negative, as minerals into gold and not–gold.
3. Astron. The aspect of the moon, Mercury, or Venus, at first and last quarter, when half the apparent disk is illuminated.
4. Bot. a A forking in pairs, as the stem of a plant; successive bifurcation. b A system of branching in which each successive axis forks or bifurcates into two equally developed branches. [<Gk. dichotomia <dicho- in two + temnein cut]