di·chot·o·my / dīˈkätəmē/ • n. (pl. -mies) [usu. in sing.] a division or contrast between two things that are or are represented as being opposed or entirely different: a rigid dichotomy between science and mysticism. ∎  Bot. repeated branching into two equal parts.

dichotomy Any variable which has only two categories. In theory these categories are meant to be mutually exclusive. The variable ‘sex’, with its two categories of ‘male’ and ‘female’, is a good example. There are numerous well-known examples of dichotomies in sociology: Tönnies's Gemeinschaft and Gesellschaft, Durkheim's mechanical and organic solidarity, and so on. A variable with more than two categories is called a polytomy. Sometimes, in order to simplify analysis, polytomous variables are collapsed—the number of categories is reduced by merging adjacent codes—to a dichotomy.

dichotomy division into two parts. XVII. — Gr. dikhotomíā, f. dikhótomos cut in two, equally divided, f. dikho-, comb. form of díkha in two, rel. to dís (see DI- 2) — -TOMY.
So dichotomize XVII.