Ordinal numbers are words that describe the order or position of things in a list or sequence. While cardinal numbers tell us how many (one, two, three), ordinal numbers tell us which one (first, second, third). Ordinals help us understand rank, sequence, and placement, which are essential in everyday communication, instructions, directions, and descriptions.
For example, if someone says, “I live on the third floor,” the word third does not tell you how many floors the building has — it tells you the exact position of the floor where they live.
How Ordinal Numbers Are Formed
In English, most ordinal numbers are formed by taking the cardinal number and adding -th:
- four → fourth
- six → sixth
- ten → tenth
- twenty → twentieth
However, the first three ordinal numbers are irregular:
1 → first
2 → second
3 → third
These irregular forms must be memorized because they do not follow the normal “-th” pattern.
There are a few spelling changes to remember:
- Numbers ending in y change the y to i before adding -eth:
twenty → twentieth - Numbers ending in ve usually change the v to f:
five → fifth - Numbers ending in ht drop the t:
eight → eighth
These changes ensure the word sounds natural when spoken.
Using Ordinal Numbers in Sentences
Ordinal numbers are often used:
1. To show order or ranking
- She finished in first place in the race.
- The second chapter of the book explains the rules.
- This is the fifth time I’ve called today.
2. To describe dates
In English, dates are spoken using ordinal numbers:
- July 4 → “July fourth”
- December 25 → “December twenty-fifth”
When written, dates often appear with superscripts:
- 1st, 2nd, 3rd, 4th, 5th …
- 21st, 22nd, 23rd, 24th …
- 31st
Examples:
- My birthday is on the 12th of March.
- Our exam is scheduled for the 31st of May.
3. To describe floors in buildings
- Our office is on the ninth floor.
- He lives on the first floor.
- The restaurant is on the twenty-second floor.
4. To describe order in time
- This is the third time I’ve watched this movie.
- The first person to arrive can choose the seats.
- I will take the second bus.
5. In instructions and steps
Instructions often use ordinal numbers to show the sequence clearly:
- First, wash your hands.
- Second, chop the vegetables.
- Third, heat the pan.
This makes actions easy to follow in the correct order.
Patterns in Higher Ordinal Numbers
After “third,” all ordinal numbers ending in 1, 2, and 3 follow a special pattern:
- 21 → twenty-first
- 22 → twenty-second
- 23 → twenty-third
- 24 → twenty-fourth
- 31 → thirty-first
So the rule for these is:
- Numbers ending in 1 → -first
- Numbers ending in 2 → -second
- Numbers ending in 3 → -third
But remember that 11th, 12th, and 13th do not follow this; they stay with -th:
- 11 → eleventh
- 12 → twelfth
- 13 → thirteenth
Example sentences:
- My desk is the 22nd desk from the door.
- She won 21st place.
- His birthday is on the 13th.
Common Mistakes to Avoid
1. Mixing cardinal and ordinal forms
Incorrect: I live on the three floor.
Correct: I live on the third floor.
2. Forgetting spelling changes
Incorrect: fiveth
Correct: fifth
3. Using “one” instead of “first” when describing order
Incorrect: I am the one in line.
Correct: I am the first in line.
4. Using cardinal numbers for dates
Incorrect: Today is July four.
Correct: Today is July fourth.
Why Ordinal Numbers Matter
Ordinal numbers are essential because they add clarity. Imagine trying to give directions without them:
- “Take the third right.”
Without ordinal numbers, you’d only say “Take right,” which is not very helpful.
They help in storytelling (“He opened the first box but ignored the second”), planning (“This is the third step”), and ranking (“She came in second place”). Without ordinals, communication would become confusing, especially when order matters.
