(Canada, US) A telephone number for which an extra charge is assessed, part of which is returned to the owner of the number.

(computing) Any computing application that requires large amounts of numerical calculation.

(mathematics) A mathematician who specializes in number theory

plural of number theorist

(euphemistic, usually childish) Feces; the act of defecation. / (nautical, slang) A first mate. / A primary assistant; vice-leader.

(graph theory) The smallest number of colours needed to colour a given graph (i.e., to assign a colour to each vertex such that no two vertices connected by an edge have the same colour).

(mathematics) a positive integer

(library science) An identification number, usually consisting of a combination of numbers and characters, used to identify and locate materials within a library.

(mathematics) A positive integer that is the product of three distinct prime factors.

Any of a range of European abbreviations for food additives used on labels. / (Britain, Ireland, informal) Any such additive, often regarded as undesirable.