English Numerals - Ordinal Numbers

Ordinal Numbers

See also: Numbering of storeys in buildings

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

0th	zeroth or noughth (see below)	10th	tenth
1st	first	11th	eleventh
2nd	second	12th	twelfth (note "f", not "v")	20th	twentieth
3rd	third	13th	thirteenth	30th	thirtieth
4th	fourth	14th	fourteenth	40th	fortieth
5th	fifth	15th	fifteenth	50th	fiftieth
6th	sixth	16th	sixteenth	60th	sixtieth
7th	seventh	17th	seventeenth	70th	seventieth
8th	eighth (only one "t")	18th	eighteenth	80th	eightieth
9th	ninth (no "e")	19th	nineteenth	90th	ninetieth

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.

21st	twenty-first
25th	twenty-fifth
32nd	thirty-second
58th	fifty-eighth
64th	sixty-fourth
79th	seventy-ninth
83rd	eighty-third
99th	ninety-ninth

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:

If the units digit is:	0	1	2	3	4	5	6	7	8	9
write this after the number	th	st	nd	rd	th	th	th	th	th	th

• 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".