Why the Spelling of 40th Causes Confusion
The correct 40th spelling is fortieth. This answer looks simple, yet it causes frequent uncertainty because the word four contains the letter u, while forty and fortieth do not. Writers often produce fourty or fourtieth by following the visual pattern of four, fourteen, and fourth. Standard English, however, treats forty as the established cardinal form and fortieth as its ordinal form.
The distinction matters in more places than birthday invitations. Students use ordinal numbers in assignment instructions, chapter labels, rankings, historical references, data descriptions, and numbered procedures. Researchers may refer to the fortieth participant, a fortieth-day observation, or the fortieth item in an instrument. Professionals use the same form in reports, anniversary communications, meeting records, and formal correspondence. A small spelling error can distract readers, weaken presentation quality, or create inconsistency across a carefully prepared document.
The spelling also illustrates an important word-formation rule. When a cardinal number ending in y becomes an ordinal, the y usually changes to ie before th is added. Thus, twenty becomes twentieth, thirty becomes thirtieth, and forty becomes fortieth. Understanding that pattern is more useful than memorizing one isolated answer because it helps with several ordinal spellings.
This guide explains the difference between cardinal and ordinal numbers, shows how to write 40th in words, compares common incorrect forms, and provides examples for academic, professional, and everyday contexts. It also covers hyphenation in compound ordinals such as forty-first, the choice between numerals and words, and proofreading methods that reduce recurring number-style errors. Writers preparing longer work can also use professional proofreading support when spelling, grammar, and consistency need a complete review.
Quick Answer: What Is the Correct 40th Spelling?
The correct spelling is fortieth. The forms fourtieth, fourtieth, and fortyth are incorrect in standard English.
Start with forty, change the final y to ie, and add th: forty → fortie + th → fortieth. Use 40th when a numeral is more suitable and fortieth when the number is written in words.
Key Takeaways
- Fortieth is the correct word form of 40th.
- Fourtieth is incorrect, even though four contains a u.
- Forty is a cardinal number; fortieth is an ordinal number.
- The final y in forty changes to ie before th is added.
- Compound ordinals are hyphenated: forty-first, forty-second, and forty-ninth.
- Both 40th and fortieth can be correct, depending on style and context.
What This Page Covers
- Correct spelling and pronunciation
- Forty versus fortieth
- Ordinal-number formation
- Sentence examples
- Hyphenation rules
- Academic style choices
Methodology and Academic Sources
This guide follows established English spelling and number-style conventions used in dictionaries, educational references, and major editorial style systems. Because individual universities, journals, and organizations may apply different numeral rules, writers should check the style guide required for their document.
For further verification, consult reputable references such as the Merriam-Webster entry for fortieth, the Cambridge Dictionary definition, and your required academic style manual. Contentxprtz applies the relevant style consistently during English editing and proofreading.
What Does “Fortieth” Mean?
Fortieth means occupying position number 40 in a sequence, or representing one of forty equal parts. It is the ordinal form of the cardinal number forty.
Cardinal number: forty
Shows quantity. Example: Forty participants completed the survey.
Ordinal number: fortieth
Shows position. Example: The fortieth participant completed the survey.
The difference changes meaning. “Forty pages” tells the reader how many pages exist. “The fortieth page” points to one page at a particular position. In mathematical language, one fortieth can also describe one part when a whole is divided into forty equal parts.
Why Is Fortieth Spelled Without the Letter “u”?
Fortieth has no u because it is formed from the standard spelling forty, not directly from four. Although related words retain the u, modern English standardized the form forty.
This is an irregular-looking feature of English rather than a sign that the word is unrelated to four. The spelling history developed over time, and the version without u became conventional. For present-day writing, the practical rule is straightforward: write four, fourteen, and fourth with u, but write forty and fortieth without it.
How Do You Form the Word “Fortieth”?
To form fortieth, change the final y in forty to ie and add th. This is the same pattern used for other multiples of ten that end in y.
- Begin with the cardinal number forty.
- Remove the final letter y.
- Add ie to create the base fortie-.
- Add the ordinal ending th.
- Check the final spelling: fortieth.
| Cardinal | Change | Ordinal | Numeral form |
|---|---|---|---|
| twenty | y → ie + th | twentieth | 20th |
| thirty | y → ie + th | thirtieth | 30th |
| forty | y → ie + th | fortieth | 40th |
| fifty | y → ie + th | fiftieth | 50th |
| ninety | y → ie + th | ninetieth | 90th |
Fortieth, Fourtieth, or Fortyth: Which Form Is Correct?
Only fortieth is correct in standard English. The other forms arise from understandable but incorrect spelling assumptions.
| Form | Status | Why |
|---|---|---|
| fortieth | Correct | Standard ordinal form of forty. |
| fourtieth | Incorrect | Incorrectly inserts the u from four. |
| fortyth | Incorrect | Fails to change final y to ie. |
| fourtieth | Incorrect | Combines the extra u with an incorrect base assumption. |
| 40th | Correct numeral form | Suitable where numerals fit the required style. |
Spell-checking software usually flags the incorrect forms, but not every document workflow catches them. Text placed in images, charts, presentation graphics, or scanned files may escape automated checks. Manual proofreading remains important, particularly when ordinal numbers appear in titles, captions, headings, certificates, or publication metadata.
How to Use 40th or Fortieth in a Sentence
Use 40th as the compact numeral form and fortieth as the fully written word form. The meaning is the same, but the choice depends on tone, layout, and editorial style.
Everyday examples
- We are planning her 40th birthday.
- The organization celebrated its fortieth anniversary.
- He finished in 40th place.
- This is the fortieth book in the archive.
Academic and research examples
- The fortieth participant was excluded because the consent form was incomplete.
- Measurements were repeated on the 40th day.
- Refer to the fortieth item in the questionnaire.
- The result appears in the 40th row of the supplementary table.
Professional examples
- The board approved the proposal at its fortieth meeting.
- The company marked its 40th year of operation.
- Please review the fortieth clause before signing.
- The candidate ranked 40th in the final list.
Do You Hyphenate Forty-First, Forty-Second, and Other Compound Ordinals?
Yes. Compound ordinals from twenty-first through ninety-ninth are normally hyphenated when written in words. The multiple of ten and the final ordinal unit work together as one compound number.
| Numeral | Correct word form | Example |
|---|---|---|
| 40th | fortieth | the fortieth chapter |
| 41st | forty-first | the forty-first chapter |
| 42nd | forty-second | the forty-second chapter |
| 43rd | forty-third | the forty-third chapter |
| 49th | forty-ninth | the forty-ninth chapter |
Notice that fortieth changes the ending of forty, whereas forty-first keeps the complete word forty and adds a hyphen plus the ordinal unit. Do not write fortieth-first.
Should Academic Writing Use “40th” or “Fortieth”?
Academic writing may use either form, but the required style guide and sentence function should control the choice. Numerals are common in statistical, scientific, tabular, chronological, and measurement-heavy contexts. Words may suit narrative prose, formal ceremonial references, or a sentence that begins with the ordinal.
Use 40th when
The number appears in a table, ranking, date-like label, experimental sequence, figure reference, compact heading, or technical description.
Use fortieth when
The sentence is primarily narrative, the number begins the sentence, or the chosen style prefers words for non-technical ordinals.
Consistency is essential. A thesis should not move randomly between 40th participant and fortieth participant unless the contexts genuinely call for different treatment. Consult the university handbook, journal author instructions, or the designated style manual. During research paper editing, an editor can check whether number treatment is internally consistent and aligned with the target publication.
Practical Examples and Mini Case Studies
These examples show how a small spelling choice can affect clarity and professionalism in real documents.
A doctoral chapter heading
Situation: A PhD scholar labels a subsection “The Fourtieth-Day Follow-Up.”
Problem: The extra u creates a visible spelling error in a heading.
Better approach: Use “The Fortieth-Day Follow-Up” or “The 40th-Day Follow-Up,” depending on the style guide. The compound modifier fortieth-day is hyphenated before the noun.
Editorial value: A full thesis proofread checks headings, tables, captions, and appendices—not only body paragraphs.
A participant reference
Situation: A researcher writes “Forty participant withdrew.”
Problem: The sentence unintentionally states a quantity and is grammatically incomplete.
Better approach: Write “The fortieth participant withdrew” for position, or “Forty participants withdrew” for quantity.
Editorial value: Context-sensitive editing distinguishes spelling from meaning and prevents a numerical statement from being misread.
An anniversary announcement
Situation: A company alternates among “40th anniversary,” “fortieth anniversary,” and “fourtieth anniversary.”
Problem: One form is incorrect and the remaining two are inconsistently styled.
Better approach: Select either “40th anniversary” or “fortieth anniversary” as the house style and apply it across invitations, banners, emails, and web copy.
Editorial value: Copyediting creates consistency across all communication assets.
Common Mistakes to Avoid
Most mistakes come from copying the spelling of four, forgetting the y-to-ie change, or mixing cardinal and ordinal meanings.
1. Writing “fourtieth”
This is the most common error. Remember that the base is forty, not fourty.
2. Writing “fortyth”
English does not simply attach th to forty. Change the final y to ie first.
3. Confusing quantity with position
Use forty to answer “how many?” and fortieth to answer “which position?”
4. Omitting hyphens in compound ordinals
Write forty-first, not forty first, when the compound ordinal is written as a number word.
5. Using the wrong suffix with numerals
The numeral is 40th, not 40st, 40nd, or 40rd. The ending follows the final spoken part: fortieth.
6. Switching styles without reason
In a formal document, choose a consistent approach for comparable uses. A proofreader should verify number style across text, tables, figures, and references.
40th Spelling and Number-Style Checklist
Before submitting or publishing
- Confirm that the base word is forty, without a u.
- Write the ordinal word as fortieth.
- Use 40th only where numeral style is appropriate.
- Check whether the number indicates quantity or position.
- Hyphenate compound forms such as forty-first.
- Use the same style for comparable references throughout the document.
- Review headings, captions, tables, figures, and graphics separately.
- Check the required university, journal, publisher, or organizational style guide.
How Is “Fortieth” Pronounced?
Fortieth is generally pronounced in three syllables: FOR-tee-uth. The exact vowel quality varies across accents, but the word normally begins like forty and ends with the soft ordinal sound heard in words such as twentieth and thirtieth.
Pronunciation can feel awkward because the ending brings several sounds close together. Speakers sometimes shorten or blur the middle of the word in rapid conversation. That variation does not change the spelling. In a presentation, recorded lecture, viva, conference talk, or professional ceremony, pronounce the word slowly enough for the ordinal meaning to remain clear.
A useful practice method is to separate the word into two parts: forty + eth. Say the cardinal number first, then add the ordinal ending without inserting an extra syllable for the letter u. Reading a complete phrase can also feel more natural: the fortieth anniversary, the fortieth participant, or the fortieth page.
Easy Ways to Remember the Correct Spelling
The best memory strategy is to learn forty first and then apply the y-to-ie ordinal rule. Trying to build the word directly from four encourages the incorrect form fourtieth.
Use the base-word method
Write forty. Cross out the final y. Replace it with ie. Add th. The result is fortieth.
Compare the pattern
Place twentieth, thirtieth, fortieth, and fiftieth together. The repeated ending makes the pattern visible.
Use a contrast sentence
“Forty people attended, and the fortieth person arrived late.” Quantity uses forty; position uses fortieth.
Check the numeral
The written form 40th ends in th, reminding you that the full word is an ordinal rather than the cardinal forty.
Writers who repeatedly make this error can add fourty and fourtieth to a custom proofreading checklist. A simple find operation across the final document can reveal mistaken forms in body text. Remember to inspect text inside figures, screenshots, tables, and design files separately because ordinary document search may not detect those elements.
Formatting 40th in Dates, Titles, Headings, and Labels
The spelling remains the same, but capitalization and numeral choice change according to placement. In ordinary sentences, use lowercase fortieth. In a title or heading, capitalize it only when the selected title style requires capitalization.
| Context | Recommended example | Editorial note |
|---|---|---|
| Sentence | the fortieth anniversary | Lowercase unless a proper name is involved. |
| Title case heading | The Fortieth Anniversary Report | Capitalize according to the title-style rules. |
| Compact label | 40th Anniversary | Useful for banners, charts, and limited space. |
| Research sequence | the 40th observation | Numerals often improve scanability in technical prose. |
| Sentence opening | The fortieth observation showed... | Avoid beginning formal prose with “40th” where the style discourages numerals at the start. |
Dates require special attention because regional conventions differ. In ordinary American English prose, writers commonly use “June 40th” only in hypothetical examples because June has thirty days; actual dates should of course be valid. In formal academic references, dates are often written without ordinal suffixes, such as “25 June 2026” or “June 25, 2026.” Therefore, do not add th automatically to every date numeral. Follow the document’s date style rather than treating all date numbers as spoken ordinals.
How Contentxprtz Can Help With Spelling and Academic Consistency
A single ordinal-number error is easy to fix, but repeated inconsistencies often signal the need for a broader language review. Academic documents can contain thousands of decisions involving spelling, capitalization, hyphenation, abbreviations, number style, citations, tables, and discipline-specific terminology.
Contentxprtz supports students, PhD scholars, researchers, authors, and professionals with ethical language editing and proofreading. The goal is not to replace the author’s ideas but to make the intended meaning clearer, more consistent, and easier to read. Depending on the document, support may include grammar correction, spelling checks, sentence-level clarity, number-style consistency, formatting review, and alignment with journal or university instructions.
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Summary: 40th Spelling
The correct word form of 40th is fortieth. It is based on forty, which is spelled without the letter u. To form the ordinal, change the final y in forty to ie and add th. Use forty for quantity and fortieth for position. Use hyphens in compound ordinals such as forty-first and forty-second.
Both 40th and fortieth can be correct; the best choice depends on context and style. In academic and professional writing, apply one consistent convention and check the relevant style guide. Avoid fourtieth, fourtieth, and fortyth.
Frequently Asked Questions
These answers address the most common searches about how to spell and use 40th.
What is the correct spelling of 40th?
The correct spelling of 40th is fortieth. It is formed from forty, but the final y changes to ie before the ordinal ending th is added.
Is it fourtieth or fortieth?
Fortieth is correct. Fourtieth is a common misspelling caused by assuming that forty keeps the u found in four. Standard English spells the cardinal number as forty and the ordinal as fortieth.
Why is 40 spelled forty without a u?
Modern standard English uses forty without a u. The form developed historically and became standardized, even though related words such as four and fourteen retain the letter u.
How do you write 40th in words?
Write 40th in words as fortieth. For example: She celebrated her fortieth birthday, or this is the fortieth page of the report.
Can I write 40th instead of fortieth in academic writing?
Both forms can be correct, but style and context matter. Formal prose often spells out smaller or non-technical ordinal numbers, while tables, dates, rankings, measurements, and compact references commonly use numerals.
How do you pronounce fortieth?
Fortieth is commonly pronounced FOR-tee-uth, with three syllables. Pronunciation varies slightly by accent, but the spelling remains fortieth.
What is the difference between forty and fortieth?
Forty is a cardinal number showing quantity. Fortieth is an ordinal number showing position or sequence. Forty students describes how many; the fortieth student identifies one position.
Should 40th have a hyphen?
The single word fortieth does not take a hyphen. Compound ordinals from twenty-first through ninety-ninth are normally hyphenated, such as forty-first and forty-second.
Is 40th correct for birthdays and anniversaries?
Yes. You can write 40th birthday, fortieth birthday, 40th anniversary, or fortieth anniversary. Choose the form that matches the tone and style of the document.
How can I avoid ordinal spelling mistakes?
Check the base number first, remember that forty has no u, change final y to ie before th, and proofread nearby compound forms such as forty-first and forty-ninth.
Write Fortieth With Confidence
The spelling becomes easy once you separate four from the standard number word forty. Start with forty, change y to ie, and add th: fortieth. Then choose between 40th and fortieth according to the style and purpose of your sentence.
For an isolated sentence, this rule may be all you need. For a thesis, research paper, manuscript, report, or publication submission, a broader check can ensure that spelling, grammar, number style, headings, tables, and references remain consistent throughout.
Correct form: fortieth. Clear rule: forty → fortieth.