Also called cardinal numeral.any of the numbers that express amount, as one, two, three, etc. (distinguished from ordinal number).

Also called potency, power. Mathematics. a number or symbol analogous to the number of elements in a finite set, being identical for two sets that can be placed into one-to-one correspondence: The cardinal number of the set a1, a2, … an is n.

1590s, "one, two, three," etc. as opposed to ordinal numbers "first, second, third," etc.; so called because they are the principal numbers and the ordinals depend on them (see cardinal (adj.)).