number

Concise Oxford English Dictionary © 2008 Oxford University Press:
number/ˈnʌmbə(r)/

▶noun

• 1 an arithmetical value, expressed by a word, symbol, or figure, representing a particular quantity.

• 2 a quantity or amount.

  ■ (a number of) several.

  ■ (numbers) a large quantity or amount; numerical preponderance.

• 3 chiefly Brit. a single issue of a magazine.

• 4 a song, dance, or other musical item.

• 5 informal an item of clothing of a particular type: a little black number.

• 6 a grammatical classification of words that consists typically of singular and plural.

▶verb

• 1 amount to.

• 2 assign a number to.

  ■ count.

• 3 include as a member of a group.

– phrases
by numbers following simple instructions identified or as if identified by numbers.
someone's (or something's) days are numbered someone or something will not survive or remain in power for much longer.
do a number on N. Amer. informal deceive or disparage.
have someone's number informal understand a person's real motives or character.
one's number is up informal one is doomed to die or suffer some other disaster or setback. [with ref. to a lottery number or a number by which one may be identified.]
without number too many to count.

– derivatives
numberless adjective.

– origin ME: from OFr. nombre (n.), nombrer (v.), from L. numerus.

usage: The construction the number of + plural noun is used with a singular verb (as in the number of people affected remains small). By contrast, the apparently similar construction a number of + plural noun is used with a plural verb (as in a number of people remain to be contacted).