Ordinal Numbers

Definition and Examples

Close-Up Of Number 5 Candle On Birthday Cake
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An ordinal number is a number that indicates position or order in relation to other numbers: first, second, third, and so on. Author Mark Andrew Lim defines ordinal numbers:

"Ordinal numbers do not represent quantity, but rather indicate rank and position, such as the fifth car, the twenty‐fourth bar, the second highest marks, and so on," (Lim 2015).

Ordinal numbers are in direct contrast with cardinal numbers (also called natural numbers and integers), which represent countable quantities. 

Learning Ordinals

If you are teaching ordinals to English language learners or young students, introduce the concept by reviewing cardinal numbers, then continue with ordinals and compare and contrast the two concepts. Take extra care to point out ordinals that break patterns. Also, introduce the terms first and last as position vocabulary words.

Example Ordinals

All ordinal numbers carry a suffix: -nd, -rd, -st, or -th. Ordinal numbers can be written out as words (second, third) or as numerals followed by abbreviations (2nd, 3rd).

  • 1: first, 1st
  • 2: second, 2nd
  • 3: third, 3rd
  • 4: fourth, 4th
  • 5: fifth, 5th
  • 6: sixth, 6th
  • 7: seventh, 7th
  • 8: eighth, 8th
  • 9: ninth, 9th
  • 10: tenth, 10th
  • 11: eleventh, 11th
  • 12: twelfth, 12th
  • 20: twentieth, 20th
  • 21: twenty-first, 21st
  • 22: twenty-second, 22nd
  • 23: twenty-third, 23rd
  • 24: twenty-fourth, 24th
  • 30: thirtieth, 30th
  • 100: one hundredth, 100th
  • 1000: one thousandth, 1,000th
  • 1 million: one millionth, 1,000,000th
  • 1 billion: one billionth, 1,000,000,000th

How to Write Ordinal Numbers

Because ordinal numbers can either be expressed using words or numbers, it can be difficult to tell when to use which version. Luckily, author R.M. Ritter explains this in New Hart's Rules: The Handbook of Style for Writers and Editors. "Spell out ordinal numbersfirst, second, third, fourth—except when quoting from another source. In the interests of saving space, they may also be expressed in numerals in notes and references. ...

"Use words for ordinal numbers in names, and for numerical street names ... :

  • the Third Reich
  • the Fourth Estate
  • a fifth columnist
  • Sixth Avenue
  • a Seventh-Day Adventist ...

Use figures for ages expressed in cardinal numbers, and words for ages expressed as ordinal numbers or decades:

  • a girl of 15 a 33-year-old man
  • between her teens and twenties
  • in his 33rd year," (Ritter 2005).

But of course, there are many more uses for ordinal numbers than just street names and ages, and that means more rules. Here are a few more stipulations for using ordinals, provided by grammar expert Val Drumond. "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," (Dumond 2012).

Using Ordinal Numbers and Cardinal Numbers Together

Ordinal and cardinal numbers often appear together, even to quantify the same object. Auriel Douglas and Michael Strumpf break down the use of ordinal and cardinal numbers together in their book, The Grammar Bible. "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. Try reading the sentences with the ordinal and cardinal numbers reversed. They simply sound wrong," (Douglas and Strumpf 2004).

Sources

  • Douglas, Auriel, and Michael Strumpf. The Grammar Bible. 1st ed., Holt, 2004.
  • Dumond, Val. Grammar for Grownups: A Guide to Grammar and Usage for Everyone Who Has to Put Words on Paper Effectively. Muddy Puddle Press, 2012.
  • Lim, Mark Andrew. The Handbook of Technical Analysis: The Practitioner's Comprehensive Guide to Technical Analysis. 1st ed., Wiley, 2015.
  • Ritter, R. M. New Hart's Rules: The Handbook of Style for Writers and Editors. 1st ed., Oxford University Press, 2005.