A positive integer that can be divided by two, and two itself. / (mathematics) An integer that is divisible by two.

(mathematics) Any integer that produces a noninteger when divided by two

plural of Abbe number

A number that represents the reciprocal of the dispersive power of a substance with transparent qualities.

(mathematical analysis, nonstandard analysis) A hyperreal number which is not a real number.

(combinatorics) Any one of a certain set of numbers which are guaranteed to exist by Ramsey's theorem; a positive integer which is a certain function of some given multiset of positive integers, where that "certain function" is that which yields the minimal number guaranteed to exist by Ramsey's theorem.

(grammar) A grammatical number denoting a quantity of exactly two.

(mathematical analysis, number theory) Any one of the rational numbers in a sequence of such that appears in numerous contexts, including formulae for sums of integer powers and certain power series expansions.

plural of cetane number

plural of surreal number