When you see a date, a birthday, or talk about an anniversary, have you ever wondered why we add letters like "th," "nd," "st," and "rd" after the numbers? It’s all about making our numbers into ordinal numbers, which show their position in a list. But it can get confusing, especially with numbers like 20.
So, what should it be: "20st" or "20th"? Let’s break this down in a way that’s easy to understand, so you have no doubts next time you write a date or celebrate an occasion.
Ordinals are really like markers in a race. They tell us who came first, second, third and so on. But with ordinals, we’re often talking about more everyday things: days, anniversaries, floors in a building.
The correct form is 20th, not 20st. This is because ordinal numbers in English follow specific rules for their endings. Numbers ending in 1 use “st” (like 21st), those ending in 2 use “nd” (like 22nd), and those ending in 3 use “rd” (like 23rd). However, all other numbers, including those ending in 0, use “th” (like 20th).
For example, when talking about a birthday, you say “20th birthday,” not “20st birthday.” This rule helps keep number references clear and consistent in both written and spoken English.
Ordinal Suffixes
The suffix—or the little group of letters we add at the end of numbers—is what turns a plain old number into an ordinal number. These suffixes are:
- "st" used after one (1st)
- "nd" used after two (2nd)
- "rd" used after three (3rd)
- "th" used after all other numbers (4th, 5th, 6th… 10th, and so on)
Why "20th" and Not "20st"?
Think about how you say "20th"; it’s "twentieth." There’s a "th" sound at the end of the word. This is your clue; this "th" guides us to use "20th." We say "first," "second," and "third" for 1, 2, and 3, so you can see why we say "20th". It fits neatly in the pattern many numbers follow.
What if you run into complex numbers with teens and beyond? Always listen to the end sound:
- Eleventh (11th)
- Twelfth (12th)
- Thirtieth (30th)
These all end in a "th" sound, so their ordinals end in "th" too.
Common Mistakes and Examples
Sometimes, people get mixed up. You might see "20st" used instead of "20th," especially when someone is typing quickly or not thinking about the rules. Knowing the correct form helps in writing invitations, official documents, and school papers.
To put it into great examples:
- My grandmother celebrated her 50th birthday.
- I live on the 14th floor.
- Today is September 20th.
When Is It Ever "st"?
Now, let’s add a little challenge. Say we’re dealing with centuries. The "21st century" is correct. Why? We say "twenty-first century." That "first" at the end points us to use "st."
Look at these examples:
- 21st century
- 31st December
Recap of the Rules:
- Listen to the end sound of the number when spoken.
- Use "st" with first, "nd" with second, "rd" with third, and "th" with all others.
- Check the full word form like “first” or “twentieth” if you’re in doubt.
Using numbers properly in sentences makes your writing clearer and more professional. So next time you’re writing a date or mentioning an anniversary, pause for a second. Think about how it sounds, and pick the right suffix. It’s a small detail that makes your communication smoother and more correct.
Conclusion
Imagine giving directions to someone in a building. Wouldn’t it be helpful if everyone knew whether you meant the 20th floor and not some mysterious "20st" floor that doesn’t exist? It’s all about being clear and making it easy for everyone to understand. Always going for the right form, like "20th," helps everyone stay on the same page—literally and figuratively!
So remember, it’s 20th—a little thing that makes a big difference in understanding and speaking English clearly.
