dichotomy

noun

1. (countable, uncountable)A separation or division into two; a distinction that results in such a division.

   “The dichotomy between the private and the public is central to almost two centuries of feminist writing and political struggle; it is, ultimately, what the feminist movement is all about. Although some feminists treat the dichotomy as a universal, trans-historical and trans-cultural feature of human existence, feminist criticism is primarily directed at the separation and opposition between the public and private spheres in liberal theory and practice.”

   “The dichotomy between maria and highlands dominates lunar mineralogy.”

   “Despite some contradictions found in the essay, its major emphasis is laid on the politics-administration dichotomy theory. It is largely devoted to the argument concerning the separability of politics and administration. The politics-administration dichotomy initiated by Wilson was later elaborated by Frank J. Goodnow in his work, “Politics and Administration” (1900).”

   “All of this previous analysis was based on two related ideas: the classical dichotomy and monetary neutrality. Recall that the classical dichotomy is the separation of variables into real variables (those that measure quantities or relative prices) and nominal variables (those measured in terms of money).”

2. (countable, uncountable)Such a division involving apparently incompatible or opposite principles; a duality.

   “But we do not try to characterize the top and bottom parts of the brain in terms of a simple dichotomy or set of dichotomies, which was exactly what was done with the existing and well-known division of the brain into two halves: namely the left versus the right, the dominant pop-culture brain story of the last few decades. […] The dif­ferences between the left and right sides of the brain are nuanced, and simple, sweeping dichotomies do not in fact explain how the two sides function.”

3. (countable, uncountable)The division of a class into two disjoint subclasses that are together comprehensive, as the division of human into female and male.

   “But in the fallacy of false dichotomy, not only do the two alternatives fail to be jointly exhaustive, but they are not even likely. As a result, the disjunctive premise is false, or at least probably false.”

4. (countable, uncountable)The division of a genus into two species; a division into two subordinate parts.
5. (countable, uncountable)A phase of the moon when it appears half lit and half dark, for example at the quadratures.

   “The Ides of Januarius indeed, the preceding month, must have fallen on March 1 at midnight, two days before the first dichotomy of the mean new moon of that month, March 3 at midnight.”

6. (countable, uncountable)Division and subdivision; bifurcation, such as that of a stem of a plant or a vein of the body into two parts as it proceeds from its origin; often successive.

   “1969, J. F. Rigby, Permian Sphenopsids from Antarctica, Geological Survey Professional Paper 613-F, page F-9, In one forked leaf there is a distinct vein dichotomy, and the leaf boundary commences 1.5 mm above the dichotomy.”

   “In most of the creeping species with dorsiventral stems (e.g., S. kraussiana, S. laevigata) roots arise at or close to the point of dichotomy; in species like S. rupestris and S. wallichii they arise at the point of dichotomy as well as other positions and in S. selaginoides and S. spinulosa they arise from knot like swellings present at the basal portion of the stem.”