A back issue of a magazine, etc. / Anything considered old-fashioned.

Synonym of Greek numeral

(arithmetic) A set of numerals for representing numbers.

(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).

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

(idiomatic) First; foremost; best, often used after its headword.

The most important person, the one who is in charge. / Someone who is top of a ranking, who is ranked first. / Oneself, being considered foremost, as by an egoist.

A measure of the antiknock properties of an automobile fuel; isooctane having an octane number of 100, a fuel with the same antiknock properties as a mixture of 90% isooctane and 10% heptane having an octane number of 90.

plural of abstract number

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