wrong suffix of ordinal number

Worried your ordinal suffix is wrong? Read the rule, the teen exception, quick checks, hyphen/spacing notes, many real examples across work, school, and casual contexts, and ready-to-copy rewrite templates.

Quick answer: which suffix do I use?

Look at the last two digits first: 11, 12, 13 always take -th. Otherwise use the last digit: 1 → -st, 2 → -nd, 3 → -rd, everything else → -th. No space between number and suffix (write 1st, not 1 st).

Examples: 21 → 21st, 22 → 22nd, 23 → 23rd, 24 → 24th
Exception: 11 → 11th, 12 → 12th, 13 → 13th (also 111th, 112th, 113th)
Superscripted suffixes are visual only; in plain text keep suffix inline

Core rule and the 11-13 exception

Check the final two digits. If they are 11, 12, or 13, use -th. If not, use the final digit to choose -st, -nd, or -rd; anything else gets -th. This applies to any whole number: only the last two digits matter.

If the last two digits are 11, 12, or 13 → use -th.
Otherwise: last digit 1 → -st; 2 → -nd; 3 → -rd; all others → -th.

Wrong: 21th birthday →
Right: 21st birthday
Wrong: 12nd anniversary →
Right: 12th anniversary
Wrong: 3th place →
Right: 3rd place
Wrong: 111st report →
Right: 111th report
Wrong: 13rd attempt →
Right: 13th attempt
Right (clarified): 102nd edition (ends in 02, previous digit isn't 1)

Hyphenation and compound modifiers

When an ordinal + noun modifies another noun, hyphenate the whole phrase: a 21st-century study, a 3rd-place finish. If the phrase follows the noun, don't hyphenate: The study is from the 21st century.

Attributive (before noun): hyphenate → the 19th-century building
Predicative (after noun): no hyphen → the building dates from the 19th century
Keep the numeral attached to its suffix when hyphenating: 21st-century, not 21 st-century

Wrong: the 21 st century →
Right: the 21st century
Wrong: 21-st century initiative →
Right: 21st-century initiative
Usage: Our 3rd-quarter numbers will be posted Friday.

Spacing, superscripts, and typography

Never put a space between the numeral and the suffix: write 4th, not 4 th. Superscripted -th or -st is a typographic choice only. Be consistent across a document.

No space: 5th, not 5 th
Superscript is optional; choose one style for the document
At sentence start, many style guides prefer spelling out ordinals (Twenty-first) over numerals

Wrong: 7 th place →
Right: 7th place
Usage: Plain text: 6th edition; decorative: 6th (with 'th' superscripted)

Real examples: work, school, and casual (copy-paste fixes)

Below are frequent real-world cases. Use the corrected sentence exactly or swap to a spelled-out ordinal when formality requires it.

Work: reports, subject lines, status updates
School: assignments, citations, class ranks
Casual: social posts, invitations, messages

Work - Wrong: Q3 (3th quarter) revenue fell. →
Right: Q3 (3rd quarter) revenue fell.
Work - Wrong: Our 21th client signed today. →
Right: Our 21st client signed today.
Work - Correct: Please review the 2nd draft. (or
formal: the second draft)
School - Wrong: She finished 1stst in the competition. →
Right: She finished 1st in the competition.
School - Wrong: See page 12nd for the reading. →
Right: See page 12th for the reading.
School - Wrong: in the 11st chapter →
Right: in the 11th chapter
Casual - Wrong: Happy 30st birthday! →
Right: Happy 30th birthday!
Casual - Wrong: I came 3th at the race. →
Right: I came 3rd at the race.
Casual - Correct: This is my 2nd cup today (or
casual: my second cup)
Work - Wrong: 13rd iteration launched →
Right: 13th iteration launched

Try your own sentence

Test the whole sentence rather than the isolated phrase. Context often makes the correct form obvious.

How to quickly fix your sentence (rewrite templates)

Choose a template that matches tone: brief (numeral + suffix), formal (spelled out), or modifier (hyphenated).

Fast correction (brief): Replace the bad suffix. Example: '21th' → '21st'.
Formal rewrite (spelled-out): 'Twenty-first' instead of '21st' at the start of a sentence or in formal prose.
Modifier rewrite (hyphenate): '21st-century study' when used before a noun.

Rewrite - Wrong: Our 21th meeting is Tuesday. → Fix: Our 21st meeting is Tuesday.
Rewrite - Wrong: 11st place went to Sara. →
Formal: Eleventh place went to Sara.
Rewrite - Wrong: 3th draft attached. → Neutral: The 3rd draft is attached.
Rewrite - Wrong: the 21 st-century plan → Fix: the 21st-century plan
Rewrite - Wrong: Happy 30st bday! → Fix: Happy 30th birthday!

Grammar context: when to spell out ordinals and style notes

Many guides recommend spelling out ordinals under one hundred in running text (first, second, third). Use numerals for technical data, tables, and places like '3rd quarter'. Consistency matters most.

If a sentence starts with a number, spell it out or reword the sentence for clarity.

Formal prose: prefer spelled-out ordinals at sentence start (Twenty-second)
Business/data: numerals + suffix are fine (2nd estimate, 4th quarter)
Be consistent: pick a style and apply it across the document

Usage: Formal contexts may prefer 'The Fifth Amendment' over 'The 5th Amendment'.
Usage: Business reports commonly use 'Q2 (2nd quarter) revenue rose'.

Memory trick and quick checks

Mnemonic: Check the last two digits first - if they are 11, 12, 13 → -th. Otherwise use the last digit: 1=s, 2=n, 3=r (st, nd, rd); default = th.

Three-step mental check:

Step 1: Look at the last two digits. Are they 11, 12, or 13? If yes → -th.
Step 2: If not, check the last digit: 1→-st, 2→-nd, 3→-rd, otherwise→-th.
Step 3: Ensure no space between number and suffix; hyphenate only for attributive modifiers.

Check: 112 → last two digits = 12 → 112th (not 112nd)

Similar mistakes and quick corrections

Fixing ordinal suffixes often removes related errors: mixing ordinals with cardinals, wrong hyphenation, inconsistent superscripts, and date-format confusion.

Ordinal vs cardinal: 'She is 1 in her class' → 'She is 1st in her class' or 'She is first in her class'.
Dates and style: 'May 5th' is common in casual AmE; some formal guides prefer 'May 5' or 'May fifth'.
Superscript inconsistency: don't mix inline suffixes with superscripts in the same document.

Wrong: She is 1 in her class. →
Right: She is 1st in her class.
Wrong: 12nd month of the year →
Right: 12th month of the year.
Wrong: May 5th (in a formal report that prefers no suffix) →
Right: May 5 or May fifth.

FAQ

Is it 21st or 21th?

21st is correct. Use -st for numbers ending in 1 unless the last two digits are 11 (which becomes 11th).

Why do 11th, 12th and 13th break the pattern?

Those are teen numbers and always take -th. The same applies to numbers ending in 11, 12, or 13, such as 111th, 112th, 113th.

Do I put a space between the number and suffix (1st vs 1 st)?

No. Write 1st, 2nd, 3rd without a space. Superscripts are a visual option only.

Should I spell out ordinals at the start of a sentence?

Yes - many style guides prefer spelling out ordinals at sentence start (e.g., Twenty-first). Rewording is another simple fix.

How should I write dates - 'May 5' or 'May 5th'?

Both are used. Formal publications often use 'May 5' or 'May fifth' per style guidelines. Choose one format and be consistent.

Quick check before you send

Run the three-step check in your head or paste the sentence into a grammar tool. Fix the suffix, remove any space, and hyphenate only for attributive modifiers. A quick scan catches the usual errors (21th → 21st, 12nd → 12th, wrong hyphenation) and keeps your writing polished.