Number

An abstract entity used to describe quantity.

"Zero, one, −1, 2.5, and pi are all numbers."

A numeral: a symbol for a non-negative integer.

"The number 8 is usually made with a single stroke."

An element of one of several sets: natural numbers, integers, rational numbers, real numbers, complex numbers, and sometimes extensions such as hypercomplex numbers, etc.

"The equation e^{i\pi}+1=0 includes the most important numbers: 1, 0, \pi, i, and e."

(Followed by a numeral; used attributively) Indicating the position of something in a list or sequence. Abbreviations: No or No., no or no. (in each case, sometimes written with a superscript "o", like Nº or №). The symbol "#" is also used in this manner.

"Horse number 5 won the race."

To label (items) with numbers; to assign numbers to (items).

"Number the baskets so that we can find them easily."

To total or count; to amount to.

"I don’t know how many books are in the library, but they must number in the thousands."