English Numerals - Ordinal Numbers

Ordinal Numbers

Ordinal numbers refer to a position in a series. Common ordinals include:

Zeroth only has a meaning when counts start with zero, which happens in a mathematical or computer science context.

Ordinal numbers such as 21st, 33rd, etc., are formed by combining a cardinal ten with an ordinal unit.

Higher ordinals are not often written in words, unless they are round numbers (thousandth, millionth, billionth). They are written using digits and letters as described below. Here are some rules that should be borne in mind.

• The suffixes -th, -st, -nd and -rd are occasionally written superscript above the number itself.
• If the tens digit of a number is 1, then write "th" after the number. For example: 13th, 19th, 112th, 9,311th.
• If the tens digit is not equal to 1, then use the following table:

• For example: 2nd, 7th, 20th, 23rd, 52nd, 135th, 301st.

These ordinal abbreviations are actually hybrid contractions of a numeral and a word. 1st is "1" + "st" from "first". Similarly, we use "nd" for "second" and "rd" for "third". In the legal field and in some older publications, the ordinal abbreviation for "second" and "third" is simply, "d".

• For example: 42d, 33d, 23d

NB: The practice of using "d" to denote "second" and "third" is still often followed in the numeric designations of units in the US armed forces, for example, 533d Squadron.

Any ordinal name that doesn't end in "first", "second", or "third", ends in "th".