cardinal number

A number (such as 1, 2, or 3) used in counting to indicate quantity but not order.

Though not all style guides agree, the general rule is that cardinal numbers one through nine are spelled out, numbers 10 and above are written in figures. (Exceptions are made for dates, decimals, exact sums of money, pages, and percentages--all of which are generally written in figures.) In business and scientific writing, figures are used in nearly every case. See also:

• Amount and Number
• Ordinal Number

Examples and Observations:

• The cardinal numbers refer to the size of a group:
  zero (0)
  one (1)
  two (2)
  three (3)
  four (4)
  five (5)
  six (6)
  seven (7)
  eight (8)
  nine (9)
  ten (10)
  eleven (11)
  twelve (12)
  thirteen (13)
  fourteen (14)
  fifteen (15)
  twenty (20)
  twenty-one (21)
  thirty (30)
  forty (40)
  fifty (50)
  one hundred (100)
  one thousand (1,000)
  ten thousand (10,000)
  one hundred thousand (100,000)
  one million (1,000,000)
  



• "When using number words, it is important to keep the difference between cardinal numbers and ordinal numbers in mind. Cardinal numbers are counting numbers. They express absolute number without any implication of position. . . .
  
  "The ordinal numbers, on the other hand, are position numbers. They correspond to the cardinal numbers but indicate position in relation to other numbers. . . .
  
  "When a cardinal number and an ordinal number modify the same noun, the ordinal number always precedes the cardinal number:

  The first two operations were the most difficult to watch.
  
  The second three innings were quite dull.

  In the first example, the ordinal number first precedes the cardinal number two. Both first and two are determiners. In the second example, the ordinal number second precedes the cardinal number three. Both second and three are determiners."
  (Michael Strumpf and Auriel Douglas, The Grammar Bible. Owl Books, 2004)