(UK, New Zealand) A telephone number beginning with 0800; these numbers are free for the caller because the call is paid for by the company or organisation being called.

plural of number field

(mathematics) A number in the form of a ratio where the dividend equals the divisor plus one.

collective noun used to indicate a set of a particular number, for example, a dozen

(Stephanus pagination) A standard reference number for a section of a given Platonic dialogue, referring to a page in the 1578 translation of Plato’s dialogues by Henricus Stephanus.

(somewhat rare) A number theorist.

plural of number theoretician

(physics) The number of electrons in an atom or ion

(fluid mechanics) A dimensionless number defined as the ratio of a characteristic velocity to a gravitational wave velocity, used in fluid mechanics to determine the resistance of an object moving through water.

(combination puzzles, chiefly Rubik's Cube) The maximum number of moves needed to solve a puzzle using God's algorithm.