Dichotomy
in logic, a distribution or separation of ideas by pairs; the diseparation of ideas by pairs; the division of a class into two sub-classes opposed to each other by contradiction.
In botany, a term applied to that kind of branching by a constant furcation or division into two parts, as where the stem of a plant branches into two branchlets, each of which in its turn divides into others, and so on. Example, the mistletoe. The veins of toe. The veins of various ferns thus dichotomously. that phase of the moon where it appears In astronomy, bisected or is only half the quadratures. bisected or is only half illuminated, as at