A number that indicates position or order in relation to other numbers: first, second, third, and so on. See also: cardinal number.
Examples and Observations:
- All ordinal numbers carry a suffix: -nd, -rd, -st, or -th.
one hundredth (100th)
one thousandth (1,000th)
one millionth (1,000,000th)
one billionth (1,000,000,000th)
- "Do not use the ordinal (th, st, rd, nd) form of numbers when writing the complete date: January 15 is the date for the examination. However, you may use the ordinal suffixes if you use only the day: The 15th is the date for the examination. . . .
"Write out ordinal numbers when they contain just one word: third prize, tenth in line, sixtieth anniversary, fifteenth birthday. Use numerals for the others: the 52nd state, the 21st Amendment."
(Val Dumond, Grammar for Grownups. HarperCollins, 1993)
- "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.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. Try reading the sentences with the ordinal and cardinal numbers reversed. They simply sound wrong."
The second three innings were quite dull.
(Michael Strumpf and Auriel Douglas, The Grammar Bible. Owl Books, 2004)