quantum number

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of a set of real numbers assigned to a physical system that individually characterize the properties and collectively specify the state of a particle or of the system.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun quantum mechanics One of certain integers or half-integers that specify the state of a quantum mechanical system (such as an electron in an atom).