
4minute read

24th October 2018
How to Use Cardinal and Ordinal Numbers
Did you know there are different types of numbers? Two common types are “cardinal numbers” and “ordinal numbers.” And even if you don’t know what these terms mean, you probably use both in your writing regularly. Let’s take a look at how to use cardinal and ordinal numbers.
Cardinal Numbers (Numbers for Counting)
Cardinal numbers are the numbers we count with and probably what you think of first when you hear the word “number.” For example, “one,” “two,” and “three” are all cardinal numbers.
You can write these numbers as either words (e.g., eight) or numerals (e.g., 8). Typically, in formal writing, you should write numbers up to ten as words and use numerals for larger values. However, different style guides have different rules on this, so make sure to check yours if you have one.
Ordinal Numbers (Numbers for Ranking)
Ordinal numbers are used to rank or order things (e.g., first, second, third). This could include placement in a race or competition, or it could simply be the day of the month (e.g., December 1^{st}).
Let’s take a look at the first few ordinal numbers to see how they work:
 First (1^{st})
 Second (2^{nd})
 Third (3^{rd})
 Fourth (4^{th})
 Fifth (5^{th})
 Sixth (6^{th})
 Seventh (7^{th})
 Eighth (8^{th})
 Ninth (9^{th})
 Tenth (10^{th})
How to Write Ordinal Numbers
You’ll notice above that writing an ordinal number as a numeral involves adding the last two letters from the word (e.g. fourth = 4^{th}). To know which letters to add, follow this guideline:
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 If the numeral ends in 1, add “st” (e.g., twentyfirst = 21^{st})
 If the numeral ends in 2, add “nd” (e.g., thirtysecond = 32^{nd})
 If the numeral ends in 3, add “rd” (e.g., fortythird = 43^{rd})
 If the numeral ends in 4, 5, 6, 7, 8, 9, or 0, add “th” (e.g., fiftysixth = 56^{th})
The only exceptions to this are “eleventh” (11^{th}), “twelfth” (12^{th}), and “thirteenth” (13^{th}). In addition, any numeral that ends 11, 12, or 13 will end “th” when written as an ordinal number (e.g., 113^{th}). We also have a few tips to share about how to write ordinal numbers in different situations:
 Most ordinal numbers are written as words when part of a sentence, especially in formal writing, but larger values can be written as numerals.
 Letters at the end of an ordinal numeral are often written in superscript, as shown above, but this is optional (e.g., you could write either “1^{st}” or “1st”).
 Written as words, you can add “ly” to ordinal numbers (e.g., “firstly” or “secondly”). This is common when setting out steps in a process, but you should avoid “ly” endings with ordinal numbers over nine.
Nominal Numbers (Numbers That Aren’t Numbers)
Finally, you may also hear people mention “nominal” numbers. These include things like phone numbers, barcodes, and the numbers of the back of football players’ shirts: i.e., numbers that name or identify something. Nominal numbers are almost always written as numerals.
Summary: Cardinal and Ordinal Numbers
We can sum up cardinal and ordinal numbers as follows:
 We use cardinal numbers to count (e.g., one, two, three). Typically, in formal writing, you will want to write out numbers up to ten as words and use numerals for larger values.
 We use ordinal numbers to rank or order things (e.g., first, second, third). Most ordinal numbers are written as words in formal writing, but larger values can be written as numerals.
If you need help checking that you’ve used numbers correctly in your written work, moreover, get in touch with Proofed today.