Table of Contents
Quick Answer
The fastest way to know which spelling to use.
The difference between vapor and vapour comes down entirely to geography.
If you are writing for an audience in the United States, the correct spelling is vapor (with an 'o'). If you are writing for an audience in the United Kingdom, Australia, or New Zealand, the correct spelling is vapour (with a 'u').
Both words refer to the exact same thing: a gas or a substance in its gaseous state. Neither spelling is grammatically incorrect, but using the wrong one for your target region can look out of place.
Vapour vs Vapor at a Glance
A side-by-side breakdown of the key differences.
| Feature | Airplane (US) | Aeroplane (UK) |
|---|---|---|
| Standard Region | United States | United Kingdom |
| Spelling | V-A-P-O-R | V-A-P-O-U-R |
| Syllable Count | 2 (VAY-per) | 2 (VAY-puh) |
| Origin | Americanized spelling | Latin via French |
| Meaning | Gas or suspended droplets | Gas or suspended droplets |
American English: Vapor
How the word is used in the United States.
In the United States, "vapor" is the universally accepted spelling. It uses the "or" suffix, reflecting phonetic simplification. It is used by American scientists, tech companies, and everyday speakers.
Industry Standard
American scientific organizations and tech companies (like Vapor Corp) exclusively use the "vapor" spelling in their manuals and products.
Media and Publishing
Major American publications and style guides, like the AP Stylebook, follow the "vapor" spelling without exception.
British English: Vapour
How the word is used in the United Kingdom.
In the United Kingdom, "vapour" is the standard spelling. It retains the "u" suffix, a hallmark of British English spelling conventions heavily influenced by Old French. It is used universally in media, literature, and science.
Cultural Presence
The spelling is standard in British literature and science, maintained by the Royal Society of Chemistry.
Modern Usage
Though casual speech is identical, formal British writing relies on "vapour" rather than the American adaptation.
What Do Both Words Mean?
The definition remains exactly the same.
Despite the spelling difference, both "vapor" and "vapour" mean exactly the same thing. They refer to a substance in its gaseous state, or a suspension of fine liquid droplets in the air.
Core Definition
A gas or a substance that is in its gaseous state, such as water vapor.
E-Cigarettes
The substance inhaled and exhaled when using an e-cigarette or vaping device.
American English Usage
How Americans naturally use the word today.
In the US, "vapor" is used in almost every context, from casual conversation to technical scientific writing. It applies to meteorology, chemistry, and the e-cigarette industry.
Casual Conversation
"The vapor from the e-cigarette smelled like strawberries."
Technical Writing
"Water vapor is a potent greenhouse gas."
Medical Contexts
"The patient was given a vapor rub to clear their lungs."
Tech Industry
"The company specializes in vaporwave aesthetics."
British English Usage
How Britons naturally use the word today.
In the UK, "vapour" holds its ground in literature, formal writing, and everyday contexts. It is the expected spelling for all gaseous substances and e-cigarette products.
Literature and Media
"A cloud of vapour rose from the boiling kettle."
Everyday Conversation
"He was blowing vapour rings in the pub."
Academic Contexts
"The experiment measured the rate of vapour condensation."
News and Journalism
"The new vapour rub is effective against chest congestion."
Which Spelling Should You Use?
Deciding based on your audience.
The decision is entirely context-driven. If you are writing an email to an American colleague, use "vapor." If you are writing a postcard from London to your friends back in Britain, use "vapour."
Choose "Vapor" if:
You are writing for a US-based publisher, studying at an American school, or creating content primarily for an American audience.
Choose "Vapour" if:
You are submitting to a UK journal, writing for a British audience, or following Commonwealth English standards.
Formal and Professional Writing
What to do in scientific and academic contexts.
In highly formal writing, the safest approach is to match the regional standard of your publisher. In scientific research, using the correct regional spelling is strictly enforced.
Business Contracts
International scientific contracts often use "gas" to prevent ambiguity between American and British stakeholders.
Academic Research
Scientific papers regarding thermodynamics use "vapor" in US journals and "vapour" in UK journals.
Pronunciation
The spelling change does not alter the spoken word.
The spelling difference does not change the spoken word at all; both are pronounced with the same number of syllables and stress pattern.
| Word | IPA | Syllables |
|---|---|---|
| Airplane (US) | /ˈveɪ.pər/ | 2 (VAY-per) |
| Aeroplane (UK) | /ˈveɪ.pə/ | 2 (VAY-puh) |
In both American and British English, the word is pronounced with two distinct beats. The American version features a slightly harder 'r' sound at the end due to rhotic pronunciation, while the British version uses a subtler, reduced vowel sound.
Spelling Difference
A visual breakdown of the letters.
The core difference is the presence of the letter "u" right after the "o."
The American version uses just "or," while the British version retains the "our" ending, a hallmark of British English spelling derived from Old French.
Why Are the Spellings Different?
The history behind the transatlantic split.
1. The Latin and French Roots
The word comes from the Latin 'vapor' (steam, heat). It entered English via Old French, where the 'u' was often retained in the spelling (vapour).
2. Noah Webster's Reform
In 1828, Noah Webster preferred the simpler 'or' spelling to align with pronunciation and simplify the language. He cemented 'vapor' as the standard American spelling.
3. The British Standard
The UK retained the 'u' in 'vapour' due to the heavy influence of Old French and Norman scribal conventions. This '-our' vs '-or' split became a hallmark of US-UK spelling differences.
Synonyms, Antonyms & Rhyming Words
Words related to, opposite of, and sounding like vapor/vapour.
Synonyms (Similar Meaning)
Example Sentences
See how both words function in original sentences.
Here are 30 original sentences using the American spelling, "vapor."
- The vapor from the e-cigarette smelled like strawberries.
- Water vapor is a potent greenhouse gas.
- A cloud of vapor rose from the boiling kettle.
- The doctor recommended a vapor rub for my cough.
- The chemist studied the properties of the mysterious vapor.
- He blew a thick cloud of vapor into the winter air.
- The vapor pressure increased as the temperature rose.
- She bought a new vapor shop in the mall.
- The vapor trail left by the jet faded quickly.
- Mercury vapor lamps lit the street at night.
- The machine converts liquid medication into a breathable vapor.
- The vapor barrier prevents moisture from entering the walls.
- He enjoys the aesthetic of vaporwave music and art.
- The hot shower created a lot of vapor in the bathroom.
- The vapor from the dry ice rolled over the stage.
- It is just a vapor lock in the fuel line.
- She could taste the vapor on her lips.
- The vapor emission from the factory was toxic.
- He uses a vapor degreaser for machine parts.
- The vapor density is lower than air.
- A vapor compression system cools the building.
- The vapor from the stew made my mouth water.
- She used a warm vapor humidifier in her bedroom.
- The vapor phase is crucial for this reaction.
- He opened the vapor shop on Main Street.
- The vapor condensed on the cold window.
- The vapor steam cleaner sanitized the floor.
- There was a toxic vapor in the mine shaft.
- The perfume was released as a fine vapor.
- The vapor recovery system captures emissions.
Here are 30 original sentences using the British spelling, "vapour."
- The vapour from the e-cigarette smelled like strawberries.
- Water vapour is a potent greenhouse gas.
- A cloud of vapour rose from the boiling kettle.
- The doctor recommended a vapour rub for my cough.
- The chemist studied the properties of the mysterious vapour.
- He blew a thick cloud of vapour into the winter air.
- The vapour pressure increased as the temperature rose.
- She bought a new vapour shop in the high street.
- The vapour trail left by the jet faded quickly.
- Mercury vapour lamps lit the street at night.
- The machine converts liquid medication into a breathable vapour.
- The vapour barrier prevents moisture from entering the walls.
- He enjoys the aesthetic of vapourwave music and art.
- The hot shower created a lot of vapour in the bathroom.
- The vapour from the dry ice rolled over the stage.
- It is just a vapour lock in the fuel line.
- She could taste the vapour on her lips.
- The vapour emission from the factory was toxic.
- He uses a vapour degreaser for machine parts.
- The vapour density is lower than air.
- A vapour compression system cools the building.
- The vapour from the stew made my mouth water.
- She used a warm vapour humidifier in her bedroom.
- The vapour phase is crucial for this reaction.
- He opened the vapour shop on the high street.
- The vapour condensed on the cold window.
- The vapour steam cleaner sanitised the floor.
- There was a toxic vapour in the mine shaft.
- The perfume was released as a fine vapour.
- The vapour recovery system captures emissions.
Vapor in US English
Specific contexts, industry standards, and cultural data for the American spelling.
In the United States, "vapor" is the standard spelling in science, tech, and everyday writing. American scientific organizations, tech companies, and everyday speakers favor this streamlined spelling.
Scientific & Academic Standard
American scientific organizations and journals exclusively use the "vapor" spelling (e.g., vapor pressure, vapor lock).
Meteorology
In American meteorology, "water vapor" is the standard term for the gaseous phase of water in the atmosphere.
E-Cigarettes & Vaping
The term is standard in American social contexts to describe the aerosol produced by e-cigarettes, known as "vapor."
Common American Phrases
• Water vapor: Gaseous water.
• Vapor rub: A medicinal chest rub.
• Vapor lock: A fuel system issue.
• Vapor trail: A condensation trail.
Vapour in UK English
Specific contexts, industry standards, and cultural data for the British spelling.
In the UK, "vapour" is the standard spelling for all contexts. British style guides and media strictly maintain the traditional French-derived "our" ending.
Scientific & Academic Standard
British scientific organizations and journals strictly use the "vapour" spelling (e.g., vapour pressure, vapour lock).
Meteorology
In British meteorology, "water vapour" is the standard term for the gaseous phase of water in the atmosphere.
E-Cigarettes & Vaping
British literature and poetry exclusively use "vapour" to describe the aerosol produced by e-cigarettes.
Common British Phrases
• Water vapour: Gaseous water.
• Vapour rub: A medicinal chest rub.
• Vapour lock: A fuel system issue.
• Vapour trail: A condensation trail.
Related Noun Spelling Differences
Other words that differ with the our/or rule.
| US English | UK English | Meaning |
|---|---|---|
| Color | Colour | The visual property of an object. |
| Honor | Honour | High respect or privilege. |
| Neighbor | Neighbour | A person living next door. |
| Flavor | Flavour | The taste of food or drink. |
Other US–UK Spelling Differences
More words that change when you cross the pond.
Color vs. Colour
Americans use "color" for the visual property, while Britons use "colour."
Center vs. Centre
The US uses "center" for a midpoint, while the UK uses "centre."
Labor vs. Labour
American English spells it "labor," while British English uses "labour."
Catalog vs. Catalogue
The US prefers "catalog," while the UK often uses "catalogue."
Common Mistakes
Frequent errors writers make with these spellings.
Mixing spellings within the same document.
✓ Pick one regional standard and stick to it.
Why: Writing "The vapor was a thick vapour" confuses the reader and breaks the consistency of your text.
Using "vapour" in an American scientific paper.
✓ Use "vapor" for US-based journals and schools.
Why: American professors and publishers expect standard American English. Using the British spelling looks like a typo in this context.
Using "vapor" in a British scientific journal.
✓ Use "vapour" for UK audiences.
Why: British scientific publishers strictly enforce traditional spelling standards, especially in chemistry and physics.
Mispronouncing "vapour" with an "oor" sound (like in "tour").
✓ Pronounce it "VAY-puh."
Why: The 'our' in British English does not sound like 'oor.' It is a reduced vowel sound, creating a subtle ending to the word.
Assuming "vapor" and "vapour" have different meanings.
✓ Recognize that they are entirely the same word.
Why: Whether referring to gaseous water, e-cigarette aerosol, or medical steam, the meaning is identical; only the regional spelling differs.
Hyphenating the words ("vap-our").
✓ Always use a single, unhyphenated word.
Why: While early texts sometimes had different conventions, modern English treats both forms as solid compound words.
Forgetting that Canada leans British for this word.
✓ Use "vapour" for Canadian audiences, though "vapor" is understood.
Why: Despite proximity to the US, Canadian English heavily favors British spellings for '-our' vs '-or' words.
Assuming the 'u' changes the meaning.
✓ Recognize it as a purely orthographic difference.
Why: Some writers assume 'vapour' means e-cigarette mist while 'vapor' means scientific gas, but both are used interchangeably in their respective regions.
Confusing the substance with "vaper" (the person).
✓ Keep "vapor/vapour" (substance) separate from "vaper" (person).
Why: "Vaper" is a person who uses an e-cigarette. "Vapor" is the mist produced by the device. They are homophones but have entirely different meanings.
Assuming the 'or' is sharp in American English.
✓ Pronounce the American 'or' exactly like the British 'our'.
Why: The 'or' and 'our' produce the exact same soft consonant sound in this context. Neither is sharper or harsher than the other.
Writing for an International Audience
How to handle the split when writing globally.
If you are writing a blog, book, or manual for a global audience, you must pick a primary English standard. Most international organizations choose either US or UK English as their default and stick to it.
Pro Tip: Because American media and tech dominate globally, many ESL learners are more familiar with "vapor." However, if your organization is based in Europe or the Commonwealth, "vapour" is the expected standard.
Memory Tip
An easy way to remember which spelling belongs to which country.
If you struggle to remember the difference, use this simple association trick:
Notice the "u." The UK spelling keeps the "u" in "vapour." America drops the "u" for "vapor."
🎮 Mini Quiz
Test your knowledge with these interactive questions.
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Frequently Asked Questions
Quick answers to common questions.
Are 'vapor' and 'vapour' pronounced the same way?
Essentially, yes. Both are pronounced with two syllables (VAY-per / VAY-puh). The American version has a slightly harder 'r' sound, while the British version uses a reduced vowel, but the pronunciation is largely identical.
Why does America use 'vapor' instead of 'vapour'?
In the early 19th century, American lexicographer Noah Webster sought to simplify American spelling to make it distinct from British English and more phonetic. Dropping the 'u' in 'vapour' was part of this movement.
Is 'vapour' ever used in the United States?
It is very rare in modern American English. You might occasionally see it in historical texts or British literary works published in the US, but 'vapor' is the undisputed standard in America today.
What about Canada and Australia? Which spelling do they use?
Canada generally follows the British spelling ('vapour'), though American spelling is also widely understood. Australia and New Zealand follow British English and use 'vapour'.
Is 'vapor' ever a person who uses an e-cigarette (vaper)?
No. A person who uses an e-cigarette is spelled 'vaper'. 'Vapor'/'Vapour' is exclusively used for the gas or mist produced, though they are homophones.
Which spelling is older, 'vapor' or 'vapour'?
'Vapour' is the older spelling, retaining the 'u' from Old French. 'Vapor' came later as an Americanized simplification introduced by Noah Webster.
Should I use 'vapor' or 'vapour' in academic writing?
You should match the spelling to the regional standard of your audience or publisher. If you are writing for an American journal, use 'vapor'. For a British or international European journal, 'vapour' is preferred.
What is the word 'vapour' derived from?
The word comes from the Latin word 'vapor', meaning steam or heat. It entered English through Old French, which influenced the retention of the 'u' in British spelling.
Are there other words that follow this 'or' vs 'our' pattern?
Yes, this is a very common pattern. Other examples include 'color/colour', 'honor/honour', 'flavor/flavour', and 'neighbor/neighbour'.
Which word is more commonly used globally today?
Because of the dominance of the American tech and media industries, 'vapor' is recognized globally. However, 'vapour' remains the correct standard spelling in formal British, Australian, and New Zealand English.
Quick Comparison
The final verdict on vapour vs vapor.
| Factor | Airplane | Aeroplane |
|---|---|---|
| Region | USA | UK |
| Syllables | 2 | 2 |
| Safest Alternative | Gas / Steam / Mist |
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