Dividing or branching into two pieces.
Choosing between two antithetical choices, between two distinct alternatives. Classification based upon two opposites. [http://www.iop.org/EJ/abstract/0305-4470/27/14/016]
That system of classification which pertains to two opposite criteria.
exhibiting or characterized by dichotomy
“a dichotomous view of the world”
(of branching) in which the axis is divided into two branches.