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

A relationship, often permanent, formed between a male and female animal; initiated during courtship and maintained after mating.

(phonology) A pair of words differing by only one phonetic segment or suprasegment, used to prove the validity of a proposed phoneme, toneme, or chroneme.

(physics) A pair of electrons (or other fermions), of opposite spin, whose theorised behaviour is the basis of the BCS theory of superconductivity.

plural of minimal pair

An item of clothing that is worn under one's trousers or pants.

plural of linear pair

(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.

(physics) The extra binding energy associated with pairs of nucleons of the same kind; this results in nuclei having odd numbers of protons or neutrons having a lower binding energy and being less stable (than those with even numbers)