23rd or 23th is a common spelling question, but only one form is correct in standard English: 23rd. You should write 23rd birthday, 23rd of September, and September 23rd, not “23th birthday” or “September 23th.” The difference comes from ordinal numbers, ordinal suffixes, and the rules that determine when to use -st, -nd, -rd, and -th.
Understanding these rules helps you write dates, birthday messages, invitations, school assignments, and everyday emails correctly. It also clears up related mistakes, such as 21th or 21st, 22nd or 22th, 13rd or 13th, and 31st or 31th. Once you understand why 23 uses -rd, you can apply the same pattern to many other numbers.
Is It 23rd or 23th?
23rd is correct, while 23th is incorrect in standard English. The number 23 takes the ordinal suffix -rd because it ends in 3 and does not belong to the special group of numbers ending in 11, 12, or 13. Therefore, write 23rd when referring to the twenty-third day, position, birthday, or event.
Here is a quick comparison of the correct and incorrect forms.
| Incorrect spelling | Correct spelling |
| 23th | 23rd |
| 23th birthday | 23rd birthday |
| 23th September | 23rd September |
| September 23th | September 23rd |
| 23th place | 23rd place |
| 23th anniversary | 23rd anniversary |
The correct form stays the same whether you use the number in a date, a birthday greeting, a ranking, or a description of an event.
For example:
- Correct: Today is my 23rd birthday.
- Incorrect: Today is my 23th birthday.
- Correct: Our appointment is on September 23rd.
- Incorrect: Our appointment is on September 23th.
- Correct: She finished in 23rd place.
- Incorrect: She finished in 23th place.
The key is to recognize that 23rd is an ordinal number. It identifies a position in a sequence rather than simply stating a quantity.
What Does 23rd Mean?
The number 23rd means twenty-third. It identifies the position of something in an ordered sequence.
You might use it to describe:
- The twenty-third day of a month.
- A person’s twenty-third birthday.
- The twenty-third item in a list.
- The twenty-third competitor in a race.
- The twenty-third anniversary of an event.
Consider the difference between these sentences:
- “I have 23 books.” This sentence uses a cardinal number to state a quantity.
- “I am reading the 23rd book.” This sentence uses an ordinal number to identify a position.
Both sentences contain the number 23, but they communicate different information.
Is 23 a Cardinal or Ordinal Number?
The number 23 is a cardinal number, while 23rd is its ordinal form.
Cardinal numbers answer the question “How many?” Ordinal numbers answer the question “Which one in order?”
| Cardinal number | Ordinal number | Written form |
| 1 | 1st | First |
| 2 | 2nd | Second |
| 3 | 3rd | Third |
| 13 | 13th | Thirteenth |
| 21 | 21st | Twenty-first |
| 22 | 22nd | Twenty-second |
| 23 | 23rd | Twenty-third |
| 24 | 24th | Twenty-fourth |
Use 23 when counting a quantity and 23rd when identifying a position, date, or anniversary.
For example, “The class has 23 students” describes the class size. “She is the 23rd student on the register” identifies her position in the list.
Why Is 23rd Correct Instead of 23th?
English uses different suffixes to form ordinal numbers. Most numbers ending in 1 take -st, numbers ending in 2 take -nd, and numbers ending in 3 take -rd. Most other numbers take -th. However, numbers ending in 11, 12, or 13 use -th, regardless of their final digit.
This rule explains why 23 becomes 23rd, while 13 becomes 13th.
The final digit provides a useful shortcut, but you must check the last two digits before choosing a suffix.
When Do You Use -st, -nd, -rd, and -th?
The four main ordinal suffixes are -st, -nd, -rd, and -th. Each appears in specific number patterns.
| Ordinal suffix | Common pattern | Examples |
| -st | Numbers ending in 1, except those ending in 11 | 1st, 21st, 31st, 41st |
| -nd | Numbers ending in 2, except those ending in 12 | 2nd, 22nd, 32nd, 42nd |
| -rd | Numbers ending in 3, except those ending in 13 | 3rd, 23rd, 33rd, 43rd |
| -th | Most other numbers, including those ending in 11, 12, and 13 | 4th, 10th, 11th, 12th, 13th, 24th |
These patterns work for large numbers, too.
For example:
- 101st, not 101th.
- 102nd, not 102th.
- 103rd, not 103th.
- 111th, not 111st.
- 112th, not 112nd.
- 113th, not 113rd.
- 123rd, not 123th.
The last three examples show why you must check the final two digits. Although 111 ends in 1, its correct ordinal form is 111th because it ends in 11. The same exception applies to 112 and 113.
A simple rule to remember: Check the last two digits first. If they are 11, 12, or 13, use -th. Otherwise, choose the suffix based on the final digit.
Why Do 11th, 12th, and 13th Use -th?
The numbers 11th, 12th, and 13th are exceptions to the usual final-digit pattern. Although they end in 1, 2, and 3, respectively, their correct ordinal forms all use -th.
Compare these numbers:
- 11th, not 11st.
- 12th, not 12nd.
- 13th, not 13rd.
- 21st, not 21th.
- 22nd, not 22th.
- 23rd, not 23th.
This distinction matters because the final digit alone does not determine every ordinal suffix.
For example, a person might correctly write “I finished in 3rd place” but incorrectly assume that 13 must become 13rd. The exception prevents that mistake.
The same principle applies to larger numbers. You write 113th because its last two digits are 13, but 123rd because its last two digits are 23.
Is It 23rd or 23th Birthday?
23rd birthday is the correct expression. It refers to the twenty-third anniversary of someone’s birth. The word birthday identifies the annual occasion, while 23rd specifies which birthday the person is celebrating. Use this form in birthday cards, party invitations, social media captions, and everyday conversation.
Here are a few natural examples:
- Happy 23rd birthday! I hope your year brings plenty of happiness.
- We’re planning a surprise party for her 23rd birthday.
- He celebrated his 23rd birthday with friends and family.
- Join us as we celebrate Alex’s 23rd birthday.
- I can’t believe my 23rd birthday is already here!
In every example, 23rd is correct because the number identifies the position of the birthday in the person’s life.
Writing “23th birthday” is a spelling error, even if the intended meaning remains understandable.
How to Write 23rd Birthday in a Sentence
The correct format depends on how you use the expression. The ordinal form remains 23rd, but the surrounding words can change.
For a birthday greeting:
- Happy 23rd birthday!
- Wishing you an amazing 23rd birthday.
- Have the best 23rd birthday ever!
a party invitation:
- Please join us to celebrate Emma’s 23rd birthday.
- You’re invited to Daniel’s 23rd birthday party.
- The celebration for my 23rd birthday begins at 7 p.m.
For a social media caption:
- Chapter 23 begins today.
- Celebrating my 23rd birthday with my favorite people.
- Twenty-three looks pretty good so far!
The phrase “Chapter 23 begins today” is a creative caption rather than a literal statement about the birthday’s ordinal form. If you want to state the age or birthday directly, use 23rd birthday or turning 23.
Is 23rd Birthday Grammatically Correct?
Yes. 23rd birthday is grammatically correct because the ordinal number modifies the noun birthday. The expression identifies which birthday someone is celebrating.
However, 23rd birthday and 23 years old do not serve exactly the same grammatical purpose.
| Expression | Meaning | Example |
| 23rd birthday | The twenty-third birthday celebration | My 23rd birthday is next week. |
| 23 years old | A person’s age | I am 23 years old. |
| Turning 23 | Reaching the age of 23 | She is turning 23 tomorrow. |
| 23rd year | The twenty-third year in a sequence or period | The organization entered its 23rd year. |
A common mistake is to use the ordinal form when stating an age.
For example:
- Correct: “I am 23 years old.”
- Incorrect: “I am 23rd years old.”
- Correct: “Today is my 23rd birthday.”
- Incorrect: “Today is my 23th birthday.”
Remember that age is usually expressed with a cardinal number, while a birthday anniversary takes an ordinal number.
Is It 23rd or 23th of September?
23rd of September is correct, while 23th of September is incorrect. You can also write the date as 23rd September or September 23rd. The first two formats are common in British English, while the month-first format is common in American English. All use the same correct ordinal form.
Here are the most common formats:
| Date format | Example |
| Day–month | 23rd September |
| Day–month with “of” | 23rd of September |
| Month–day | September 23rd |
| Numerical date | September 23 or 09/23, depending on context |
The ordinal suffix is necessary when you choose to write the date with an ordinal number. However, you do not have to use the suffix in every written date.
For example, September 23 is also correct. Many style guides prefer cardinal numerals without ordinal suffixes in dates, particularly in formal American writing.
Compare these sentences:
- “My appointment is on September 23.”
- “My appointment is on September 23rd.”
- “My appointment is on the 23rd of September.”
All three communicate the date clearly.
The important point is to avoid 23th.
23rd or 23th October
The correct forms are 23rd October and October 23rd. Both refer to the twenty-third day of October.
Examples:
- Our school event takes place on 23rd October.
- The application deadline is October 23rd.
- We’re meeting on the 23rd of October.
- Her flight arrives on October 23.
You can use either day-first or month-first formatting, depending on your audience and the style of the document.
For a British audience, “23 October” is a common formal style. For an American audience, “October 23” is common. The ordinal forms are also understood in both varieties of English.
Incorrect: The meeting is scheduled for October 23th.
Correct: The meeting is scheduled for October 23rd.
23rd or 23th August
Use 23rd August or August 23rd, not “23th August.”
Examples:
- The summer program ends on 23rd August.
- Our family reunion is on August 23rd.
- Please return the completed form by August 23.
- The ceremony will take place on the 23rd of August.
If you are writing an invitation, you can make the date easy to scan by placing it on a separate line.
For example:
Summer Celebration
Saturday, August 23rd
6:00 p.m. to 9:00 p.m.
This format separates the date from the other event details. Just remember that the weekday should match the actual calendar date for the year you intend to use.
23rd or 23th June
The correct form is 23rd June or June 23rd.
Examples:
- The registration period closes on 23rd June.
- We are traveling on June 23rd.
- The final examination is scheduled for June 23.
- Her birthday falls on the 23rd of June.
These examples show that the suffix remains the same even when the month changes.
You do not need to memorize a separate rule for June, August, September, or October. Once you understand the ordinal-number rule, you can apply it to any date.
What Does 23rd Mean in a Month?
The 23rd of a month means the twenty-third calendar day of that month. It does not refer to the twenty-third month of the year. A year has 12 months, so “23rd month” usually refers to a position in a longer sequence, such as a 23-month project or a person’s twenty-third month of age.
Consider these examples:
- “The rent is due on the 23rd of each month.”
- “Our project will enter its 23rd month in December.”
- “The 23rd day of June is June 23.”
- “The baby is entering the 23rd month of life.”
The context determines what the ordinal number describes.
If you mean a date on the calendar, write the 23rd of the month or name the specific month. If you mean the twenty-third month in a sequence, write the 23rd month.
For example, “The project is now in its 23rd month” means that 23 months have passed through the project’s timeline, depending on how the project counts its starting month. It does not mean that the calendar has a twenty-third month.
23rd vs. Other Ordinal Numbers: Common Mistakes
The same rules that explain 23rd or 23th also help you correct other ordinal-number errors. Numbers ending in 1, 2, or 3 generally use -st, -nd, or -rd, respectively, but numbers ending in 11, 12, and 13 use -th. Most other numbers also use -th.
Use this table as a quick reference.
| Incorrect form | Correct form | Example |
| 21th | 21st | The 21st of May |
| 22th | 22nd | Her 22nd birthday |
| 23th | 23rd | September 23rd |
| 24rd | 24th | The 24th student |
| 13rd | 13th | October 13th |
| 31th | 31st | The 31st of December |
| 11st | 11th | November 11th |
| 12nd | 12th | December 12th |
The best way to avoid these errors is to identify the last two digits first. That step catches the most common exception before you apply the usual suffix pattern.
Is It 22nd or 22th?
22nd is correct; 22th is incorrect. The number 22 ends in 2, and it does not fall into the special 11–13 group. Therefore, it takes the ordinal suffix -nd.
Examples:
- Today is the 22nd.
- Her 22nd birthday is next month.
- The meeting is scheduled for the 22nd of October.
- He finished in 22nd place.
Compare 22nd with 12th:
- 12th is correct because 12 belongs to the exception group.
- 22nd is correct because its last two digits are 22, not 12.
The pattern also applies to 32nd, 42nd, and 52nd.
Is It 21st or 21th?
21st is correct, while 21th is incorrect. Numbers ending in 1 generally take -st, provided the last two digits are not 11.
Examples:
- The 21st of March.
- My 21st birthday.
- The 21st person in line.
- The company’s 21st anniversary.
The comparison with 11th makes the rule easier to remember.
| Number | Correct form |
| 1 | 1st |
| 11 | 11th |
| 21 | 21st |
| 31 | 31st |
| 41 | 41st |
| 111 | 111th |
| 121 | 121st |
Notice that 111th follows the exception because the number ends in 11. However, 121st uses -st because its final two digits are 21.
Is It 13rd or 13th?
13th is correct; 13rd is incorrect. Although 13 ends in 3, it belongs to the special group of numbers ending in 11, 12, and 13. These numbers use -th rather than the suffix suggested by the final digit alone.
Examples:
- The 13th of September.
- Her 13th birthday.
- The 13th chapter of the book.
- The 13th contestant in the competition.
Compare these forms:
- 3rd
- 13th
- 23rd
- 33rd
- 103rd
- 113th
- 123rd
This comparison demonstrates why the final two digits matter. The suffix changes when the number ends in 13, even when larger numbers contain the same final digit.
Is It 31st or 31th?
31st is correct, while 31th is incorrect. The number 31 ends in 1, and its final two digits are not 11. It therefore takes the suffix -st.
Examples:
- December 31st.
- The 31st day of the month.
- Her 31st birthday.
- The 31st item on the list.
You may also see dates written without ordinal suffixes, such as “December 31.” That format is correct as well.
Compare the following:
- 11th, not 11st.
- 21st, not 21th.
- 31st, not 31th.
- 111th, not 111st.
- 121st, not 121th.
The same exception explains the difference between 11th and 31st. Both numbers end in 1, but only 11 ends in the special teen-number pattern.
Is It 24rd or 24th?
24th is correct; 24rd is incorrect. Numbers ending in 4 generally take the suffix -th, so 24 becomes 24th.
Examples:
- The 24th of August.
- His 24th birthday.
- The 24th page of the document.
- The 24th participant in the race.
You can apply the same rule to 4th, 14th, 34th, 44th, and 104th.
However, the teen exception still matters for numbers ending in 14. For example, 14th is correct, as is 114th. Both end in 14, and neither takes -rd.
23rd or 23th? Examples in Everyday Writing
The easiest way to remember the correct form is to see how 23rd works in real sentences. The ordinal number can describe a date, an anniversary, a position, or an item in an ordered list. The context changes, but the correct spelling does not.
Examples of 23rd in Sentences
Here are original examples showing different uses of the number.
Dates and appointments
- Our next meeting is on the 23rd of September.
- The doctor scheduled my appointment for September 23rd.
- Please send the signed agreement by the 23rd.
- The conference begins on October 23rd.
Birthdays and anniversaries
- We’re organizing a small dinner for her 23rd birthday.
- He received a new laptop for his 23rd birthday.
- Their company will celebrate its 23rd anniversary next spring.
- She wrote a personal note to mark her 23rd birthday.
Rankings and sequences
- Maya finished in 23rd place in the race.
- Turn to the 23rd page of your workbook.
- This is the 23rd episode of the series.
- The team selected him as its 23rd player on the roster.
Work and education
- The assignment is due on the 23rd.
- Our class will discuss the 23rd chapter tomorrow.
- The application must arrive by September 23rd.
- The business entered its 23rd year of operation.
These examples show why it is useful to understand the meaning of ordinal numbers instead of memorizing a single date.
Common Errors to Avoid
Several habits can lead to incorrect ordinal forms. You can avoid most of them with a quick check.
Mistake: Adding -th to every number
Incorrect: “My birthday is on the 23th.”
Correct: “My birthday is on the 23rd.”
The suffix -th does not apply to every number. Numbers ending in 1, 2, and 3 generally use their own suffixes, with the 11–13 exception.
Mistake: Applying the final-digit rule to 13
Incorrect: “The event is on the 13rd.”
Correct: “The event is on the 13th.”
Check the last two digits before applying the general rule.
Mistake: Using an ordinal number to state an age
Incorrect: “I am 23rd years old.”
Correct: “I am 23 years old.”
Use a cardinal number when stating how old someone is. Use an ordinal number when identifying a birthday anniversary.
Mistake: Assuming every date needs an ordinal suffix
Both of these are correct:
- September 23
- September 23rd
You can use the simpler cardinal form in many formal contexts. If you choose to include an ordinal suffix, make sure you spell it correctly.
Mistake: Mixing date styles without a reason
In a single document, consistent formatting helps readers understand dates quickly. For example, use “September 23” throughout an American business document rather than switching randomly between “23 September,” “September 23rd,” and “23rd of September.”
Consistency is a style choice. The spelling rule remains the same.
Why Do People Search for 23rd or 23th on Reddit?
People may search for 23rd or 23th Reddit when they want a quick explanation from an online community or want to check whether other English users have the same question. Ordinal suffixes can seem inconsistent at first, especially when comparing 13th with 23rd. However, informal online discussions do not change the standard spelling rule: 23rd is correct.
There are several reasons this question can cause confusion:
- The suffixes vary. English uses -st, -nd, -rd, and -th.
- The exceptions seem unusual. The forms 11th, 12th, and 13th do not follow the usual final-digit pattern.
- Dates appear in different formats. Writers may see “23 September,” “September 23,” and “September 23rd.”
- Typing mistakes spread easily. A misspelling can appear in a post or comment without being correct.
If you see “23th” in an online discussion, treat it as a spelling error rather than an alternative standard form.
A useful way to remember the distinction is to compare 13th and 23rd. Both numbers end in 3, but 13 uses -th because it belongs to the exception group. The number 23 does not, so it takes -rd.
A Simple Way to Remember 23rd and Other Ordinal Suffixes
You do not need to memorize every ordinal number individually. A short three-step check will help you choose the correct form for most numbers.
Step 1: Check the last two digits.
If the number ends in 11, 12, or 13, use -th.
Examples: 11th, 12th, 13th, 111th, 112th, and 113th.
Step 2: If it is not an exception, check the final digit.
- Ends in 1: use -st.
- Ends in 2: use -nd.
- Ends in 3: use -rd.
- Ends in 0 or 4–9: use -th.
Examples: 21st, 22nd, 23rd, 24th, 30th, and 39th.
Step 3: Check the sentence.
Ask whether you need a cardinal or ordinal number.
- “There are 23 people in the room.” Use a cardinal number.
- “She is the 23rd person to arrive.” Use an ordinal number.
- “He is 23 years old.” Use a cardinal number.
- “He is celebrating his 23rd birthday.” Use an ordinal number.
This method works for dates, ages, rankings, lists, anniversaries, and many other everyday situations.
A Quick Practice Test
Choose the correct form in each sentence before checking the answers.
- My sister is celebrating her 23rd / 23th birthday.
- The deadline is September 23rd / September 23th.
- He finished in 13rd / 13th place.
- The ceremony takes place on the 31th / 31st of December.
- She celebrated her 22th / 22nd birthday last week.
Answers:
- 23rd birthday
- September 23rd
- 13th place
- 31st of December
- 22nd birthday
The first two test the primary keyword and its date usage. The remaining examples reinforce the exceptions and the related ordinal-number patterns.
Conclusion: Always Use 23rd, Not 23th
When choosing between 23rd or 23th, always use 23rd in standard English. The correct form applies to birthdays, dates, anniversaries, rankings, and ordered lists. You can write 23rd birthday, 23rd of September, 23rd October, or June 23rd without changing the ordinal suffix.
The key is to understand the pattern rather than memorize isolated words. Numbers ending in 1, 2, and 3 generally use -st, -nd, and -rd, while most other numbers use -th. Numbers ending in 11, 12, and 13 are the main exceptions.
Keep these forms in mind:
- 21st, not 21th.
- 22nd, not 22th.
- 23rd, not 23th.
- 24th, not 24rd.
- 13th, not 13rd.
- 31st, not 31th.
Before sending a birthday invitation, publishing a date, or submitting an assignment, take a moment to check the ordinal suffix. If you want to improve your everyday writing further, explore related guides on ordinal numbers, date formatting, and common English spelling mistakes.
