The Collaborative International Dictionary of English v.0.48:

Number \Num"ber\ (n[u^]m"b[~e]r), n. [OE. nombre, F. nombre, L.
   numerus; akin to Gr. no`mos that which is dealt out, fr.
   ne`mein to deal out, distribute. See Numb, Nomad, and cf.
   Numerate, Numero, Numerous.]
   1. That which admits of being counted or reckoned; a unit, or
      an aggregate of units; a numerable aggregate or collection
      of individuals; an assemblage made up of distinct things
      expressible by figures.
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   2. A collection of many individuals; a numerous assemblage; a
      multitude; many.
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            Ladies are always of great use to the party they
            espouse, and never fail to win over numbers.
                                                  --Addison.
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   3. A numeral; a word or character denoting a number; as, to
      put a number on a door.
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   4. Numerousness; multitude.
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            Number itself importeth not much in armies where the
            people are of weak courage.           --Bacon.
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   5. The state or quality of being numerable or countable.
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            Of whom came nations, tribes, people, and kindreds
            out of number.                        --2 Esdras
                                                  iii. 7.
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   6. Quantity, regarded as made up of an aggregate of separate
      things.
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   7. That which is regulated by count; poetic measure, as
      divisions of time or number of syllables; hence, poetry,
      verse; -- chiefly used in the plural.
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            I lisped in numbers, for the numbers came. --Pope.
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   8. (Gram.) The distinction of objects, as one, or more than
      one (in some languages, as one, or two, or more than two),
      expressed (usually) by a difference in the form of a word;
      thus, the singular number and the plural number are the
      names of the forms of a word indicating the objects
      denoted or referred to by the word as one, or as more than
      one.
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   9. (Math.) The measure of the relation between quantities or
      things of the same kind; that abstract species of quantity
      which is capable of being expressed by figures; numerical
      value.
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   Abstract number, Abundant number, Cardinal number, etc.
      See under Abstract, Abundant, etc.

   In numbers, in numbered parts; as, a book published in
      numbers.
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WordNet (r) 3.0 (2006):

cardinal number
    n 1: the number of elements in a mathematical set; denotes a
         quantity but not the order [syn: cardinal number,
         cardinal]

The Free On-line Dictionary of Computing (30 December 2018):

cardinal number

   The cardinality of some set.