When we’re talking about writing dates or numbers in a sequence, you might wonder how to express them properly. Have you ever received a birthday card with “Happy 9th Birthday”? That probably made sense to you, right? But what if it said “Happy 9st Birthday”? Things will seem a bit off. Let’s figure out why.
The correct form is 9th. When forming ordinal numbers, the endings -st, -nd, -rd, or -th are added to the base cardinal number. The ending depends on the last digit of the number. For instance, 1 becomes 1st, 2 becomes 2nd, and 3 becomes 3rd. However, most numbers end with -th, including 9, which becomes 9th.
Let’s look at an example: when talking about birthdays, you would say “9th birthday” not “9st birthday”. This rule helps keep your English clear and correct, especially when writing dates or placing things in order.
Understanding Ordinal Numbers
Ordinal numbers help us talk about the order or position of things, like in a race or a line. They are different from cardinal numbers, which we use just for counting, like one, two, three.
Rules for Forming Ordinals
To make an ordinal number, we usually add th, nd, rd, or st to the cardinal number. Now, isn’t that pretty straightforward? But how do we know which ending to use?
Here is the general rule: numbers ending in 1 get st, those in 2 are followed by nd, numbers that end in 3 use rd, and all the rest take th.
Examples:
- 1st (first)
- 2nd (second)
- 3rd (third)
- 4th (fourth) all the way to 10th (tenth), and beyond!
Sounds simple, doesn’t it? But, English can sometimes throw us a little twist.
Special Cases to Consider
What happens with numbers like 11, 12, and 13? Here’s where English likes to play a trick! Despite having 1, 2, and 3 as their last digits, these numbers always end in th. Therefore, we say 11th, 12th, and 13th.
So, I would count like this: 1st, 2nd, 3rd, 4th, …, 9th, 10th, 11th, 12th, 13th, and so on.
Understanding the Use of ‘st’ with 9
If you ever wonder why we don’t say 9st, it’s because of those rules we talked about. Since 9 ends in 9 (and not 1), it follows the rule of having a th at the end, making it 9th.
More Examples to Clear Things Up
- 29th (Twenty-ninth) – see how the pattern continues?
- 39th (Thirty-ninth)
- 49th (Forty-ninth), and it keeps going on like this!
Do you see the pattern? It keeps things neat and orderly!
Practical Uses of Ordinal Numbers
We use ordinal numbers a lot! Think about dates, for example. Your birthday might be on the 9th of the month. Events, places in a line, steps in instructions, and floors in a building all often use ordinal numbers too.
When to Be Extra Careful
Always double-check when writing invitations or announcements. You don’t want to confuse your guests with a “25st” anniversary celebration instead of “25th”!
And in sports? Imagine a commentator saying the runner finished “9st”. That would sound really strange!
Ready, Set, Go – Use It Right!
Now that you understand the how and why of 9th vs. 9st, try spotting these in real life. See how often and where you find ordinal numbers starting today. Sound like a fun challenge?
Can you think of any other examples or places where you might see ordinals? How about chapters in a book, or telling someone which floor to get off the elevator? There’s a lot of them once you start looking!
Always remember, understanding the small changes in how we use numbers can make your communication clearer. No one wants a confusing sign or invitation, right?
So next time you’re planning to use a number to talk about order, think back to this little talk we had. Choosing 9th over 9st won’t just sound better, it’ll make sure everyone understands you perfectly. And isn’t that what good communication is all about?
