Meaning

• 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."

• Quantity.

  "Any number of people can be reading from a given repository at a time."

• A sequence of digits and letters used to register people, automobiles, and various other items.

  "Her passport number is C01X864TN."

• A telephone number.

• (grammar) Of a word or phrase, the state of being singular, dual or plural, shown by inflection.

  "Adjectives and nouns should agree in gender, number, and case."

• (in the plural) Poetic metres; verses, rhymes.

• A performance; especially, a single song or song and dance routine within a larger show.

  "For his second number, he sang "The Moon Shines Bright"."

• A person.

• An item of clothing, particularly a stylish one.

• A marijuana cigarette, or joint; also, a quantity of marijuana bought form a dealer.

• An issue of a periodical publication.

  "the latest number of a magazine"

• A large amount, in contrast to a smaller amount; numerical preponderance.

Meaning

• 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."