dichotomy: Meaning and Definition of

di•chot•o•my

1. division into two parts, kinds, etc.; subdivision into halves or pairs.
2. division into two mutually exclusive, opposed, or contradictory groups: a dichotomy between thought and action.
3. a mode of branching by constant forking, as in some stems, in veins of leaves, etc.
4. the phase of the moon or of an inferior planet when half of its disk is visible.