What are Ordinal Numbers?
In English grammar, Ordinal Numbers (first, second, third, etc.) are words that express position or order in a sequence. They answer the specific question "which one in a series?" Unlike cardinal numbers (which tell you 'how many'), ordinal numbers tell you 'where' something is ranked. They are heavily utilized for dates, building floors, competition rankings, centuries, and listing sequences in text.
Ordinal Numbers Structure and Formula
Because ordinal numbers point out a specific position in a sequence, they act as adjectives modifying a noun, and they almost always require the definite article "the".
Standard Formula:
- The + Ordinal Number + Noun + V ...
- S + V + The + Ordinal Number
Examples: The first student arrived. / He is the first.
How to Form Ordinal Numbers (Regular Rules)
The general rule for creating an ordinal number is remarkably simple: take the base cardinal number and add the suffix -th.
| Cardinal Number | Ordinal Formation | Output | Abbreviation |
|---|---|---|---|
| four | four + th | fourth | 4th |
| six | six + th | sixth | 6th |
| seven | seven + th | seventh | 7th |
| ten | ten + th | tenth | 10th |
The Irregular First Three Ordinals
The numbers 1, 2, and 3 completely break the "-th" rule. They must be memorized, as they form the foundation for all compound numbers.
| Cardinal Number | Irregular Ordinal Form | Abbreviation Output |
|---|---|---|
| one | first | 1st |
| two | second | 2nd |
| three | third | 3rd |
Spelling Changes for Some Ordinal Numbers
While adding "-th" is the standard rule, some numbers experience slight spelling shifts to make pronunciation easier.
Dropped Letters and Vowel Shifts (5, 8, 9, 12)
| Cardinal | Ordinal Form | Spelling Change Rule |
|---|---|---|
| five | fifth | 've' changes to 'f' |
| eight | eighth | drop the extra 't' |
| nine | ninth | drop the trailing 'e' |
| twelve | twelfth | 've' changes to 'f' |
The "Y to IE" Rule (Tens: 20, 30, 40, etc.)
When a number ends in "y", change the "y" to "ie" before adding "th".
- twenty → twentieth (20th)
- thirty → thirtieth (30th)
How to Form Compound Ordinals (21st and Beyond)
When writing compound numbers (like 21, 54, 99), only the final word changes to the ordinal form. The first part remains a regular cardinal number, and you connect them with a hyphen.
| Cardinal Number | Compound Ordinal Formula | Abbreviation |
|---|---|---|
| twenty-one | twenty + first | 21st |
| twenty-two | twenty + second | 22nd |
| thirty-four | thirty + fourth | 34th |
| one hundred and one | one hundred and + first | 101st |
When to Use Ordinals in English
Dates
When speaking about dates, ordinals are mandatory, even if the written text only shows a cardinal number (e.g., March 3).
- My birthday is on the third of March / March 3rd.
- The meeting is on January 21st / the twenty-first of January.
Floors of a Building
- The office is on the fifth floor.
- She lives on the twenty-second floor.
Rankings and Positions
- She finished first in the race.
- He came third in the competition.
Centuries
- We live in the twenty-first century.
Sequences and Actions
- This is the second time I've visited.
Real-life Examples of Ordinal Numbers
- The first man on the moon landed there on July 20th, 1969. (S + V + Prep Phrase)
- She received second prize at the competition.
- Our office is on the fifteenth floor of the building.
- This is the twenty-first century — things change fast.
Summary & Cheatsheet for Ordinal Numbers
| Formation Category | Grammar Pattern | Examples |
|---|---|---|
| Base Irregulars | Must memorize entirely | 1st (first), 2nd (second), 3rd (third) |
| Standard Rule | Base Number + th | 4th (fourth), 10th (tenth) |
| Spelling Shifts | Alter vowels / drop letters | 5th (fifth), 12th (twelfth), 9th (ninth) |
| Tens (y ending) | y → ie + th | 20th (twentieth), 30th (thirtieth) |
| Compounds | Last word only changes | 21st (twenty-first), 42nd (forty-second) |
Frequently Asked Questions
Why do dates sometimes look like "March 3" but are read as "March third"?
In American English formatting, it is common to write the cardinal number (March 3) for brevity, but the spoken rule remains strict: dates require ordinal pronunciation (March third).
Do I always use "the" before an ordinal number?
Almost always, yes, because ordinals point to specific items (e.g., the first door). The main exception is in competitive rankings where the noun is dropped (He finished first.) or when using a possessive pronoun instead (My first car).
Is it twelveth or twelfth?
It is spelled twelfth. The 've' in twelve transforms into an 'f' before the 'th' is added.
How do I say large ordinal numbers like 1,000,000th?
You simply add "-th" to the very end: "one millionth". For example, "You are the one millionth customer!"