A tool for drawing accurate circles or arches, usually consisting of two arms joined at one end in such a way that the arms can be opened and closed; one of the arms is pointed at its free end while the other holds a pencil, pencil lead or some other implement for making marks.

(chiefly US, colloquial, idiomatic, somewhat vulgar) To be manly, brave.

(mathematics) a pair of integers (i,j) is an inversion pair of some permutation 𝜎 if i𝜎(j).

Two chromosomes that are identical, with the same genes.

plural of base pair

(biology) In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds.

A single girl (or, rarely, a boy), usually a foreigner, who helps a host family with childcare, housework, or both while staying as a guest with a host family, and generally receives a small allowance (or pocket money).

(geometry) The two supplementary adjacent angles formed by two intersecting lines

(set theory) An object containing exactly two elements in a fixed order, so that, when the elements are different, exchanging them gives a different object. Notation: (a, b) or ⟨a,b⟩.

(chemistry) A pair of electrons in the valence shell of an atom that does not participate in bonding.