Any of the identification numbers used in an informal system for classifying catfish before they have an scientific name.

plural of carbon number

(organic chemistry) The number of carbon atoms in each molecule of a compound.

plural of occupation number

(physics) The numerical extent to which a quantum state is filled (in a system of many, identical quantum particles)

(grammar) A noun that represents a number

(grammar) Grammatical number denoting a quantity of exactly three

plural of copy number

(astronomy) The total number of stars in the observable universe, often estimated to be in the sextillions.

Any of several forms of fixed-length identification number on stamps, books, etc.