(biology) The process whereby a cell divides asexually to produce two daughter cells.

(mathematics) a function of the type f:V⨯V→V, or more generally, a function of the type f:U_1⨯U_2⨯...⨯U_n→V in which exactly two of the sets Uᵢ are equal to V.

(astronomy) A pair of quasars which gravitationally interact with each other, unlike a standard double quasar, which does not interact.

(astronomy) A stellar system in which two stars orbit around their center of mass; double star.

A gender system in which people are categorized, in terms of gender and often also sex, exclusively as either male or female.

(computing) Either of the characters 0 and 1, used in the binary numeral system.

(computing) A number represented by the binary digits 0 and 1.

(set theory, order theory, "on" a set A) A subset of the Cartesian product A×A (the set of ordered pairs (a, b) of elements of A).

(chemistry) A chemical compound composed of only two elements. / (chemistry) A compound composed of an element and a radical (a group of atoms that behave as one piece).

(arithmetic) arithmetic using binary numbers