dichotomy

Definitions:

Division or distribution by pairs.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
A division into two parts.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
Branching which results from the division of a growing point with two equal parts.
- A dictionary of scientific terms. By Henderson, I. F.; Henderson, W. D. Published 1920. (noun) (n.) (noun)
DICHOTOMOUS.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (adjective) (adj.) (adjective)
Continuous division by pairs, especially of a class in a descending series into pairs of groups distinguished by coutradictory qualities.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)

Usage examples:

This however is not quite the case, for, in virtue of the Law of Excluded Middle, there is always open to us, independently of experience, a hypothetical division by dichotomy
- Deductive Logic by St. George Stock
Under the influence of this unreasoning terror, they plead that, in Dichotomy by Contradiction, the negative part is too large to deal with, so that it is better to regard each Thing as either included in, or excluded from, the positive part.
- Symbolic Logic by Lewis Carroll
For the purposes of Symbolic Logic, it is so much the most convenient plan to regard the two sub- divisions, produced by Dichotomy on the same footing, and to say, of any Thing, either that it " is" in the one, or that it " is" in the other, that I do not think any Reader of this book is likely to demur to my adopting that course.
- Symbolic Logic by Lewis Carroll