Tumour and tumor have the same meaning. Both words refer to an abnormal growth of cells in the body. The only difference is the spelling used in different types of English.
This often confuses students, medical writers, healthcare professionals, and English learners because both versions appear in books, research papers, and websites. American English uses one spelling, while British English prefers the other.
In this guide, you will learn the difference between tumour and tumor, their origin, British and American spelling rules, common mistakes, everyday examples, usage trends, and which spelling is best for your audience.
Quick Answer
Both tumour and tumor are correct.
- Tumor is the standard spelling in American English.
- Tumour is the standard spelling in British English.
- Both words mean an abnormal mass of tissue caused by uncontrolled cell growth.
Examples
- The doctor examined the tumor. ✅
- The doctor examined the tumour. ✅ (British English)
The Origin of Tumour or Tumor
The word comes from the Latin word tumor, meaning “swelling” or “bulge.” It entered English through Old French.
British English later adopted the spelling tumour, adding -our, which became common in many words such as colour and favour.
American English simplified many -our words to -or, making tumor the standard spelling. The meaning remained exactly the same.
British English vs American English Spelling
British English uses tumour.
American English uses tumor.
| British English | American English |
|---|---|
| tumour | tumor |
| tumour growth | tumor growth |
| brain tumour | brain tumor |
Examples
| British English | American English |
|---|---|
| The patient has a brain tumour. | The patient has a brain tumor. |
| Doctors removed the tumour. | Doctors removed the tumor. |
| The tumour was benign. | The tumor was benign. |
Which Spelling Should You Use?
Choose the spelling that matches your audience.
- Use tumor for readers in the United States.
- Use tumour for readers in the United Kingdom, Australia, New Zealand, and many Commonwealth countries.
- Medical journals usually follow the spelling style of their country.
- If you write for an international audience, follow your organization’s style guide and stay consistent.
Common Mistakes with Tumour or Tumor
Many writers accidentally mix British and American spelling.
| Incorrect | Correct |
|---|---|
| Tumour in American medical writing | Tumor |
| Tumor in British medical writing | Tumour |
| Mixing tumour and tumor in one document | Use one spelling style |
| Tumourr | Tumour or Tumor |
Tips
- Match your spelling to your audience.
- Keep the same English style throughout your writing.
- Follow your publisher’s or employer’s style guide.
Tumour or Tumor in Everyday Examples
“The doctor will discuss the tumor results tomorrow.”
“The doctor will discuss the tumour results tomorrow.” (British English)
News
“Researchers have developed a new treatment for brain tumor patients.”
Social Media
“My friend is raising money for tumor research.”
“Our local hospital supports tumour awareness campaigns.”
Formal Writing
“The tumor was successfully removed during surgery.”
“The tumour was successfully removed during surgery.”
Tumour or Tumor – Google Trends & Usage Data
Search data shows that tumor is more common worldwide because American medical websites, journals, and health resources have a large global audience.
Regional usage generally follows these patterns:
| Country | Common Spelling |
|---|---|
| United States | Tumor |
| Canada | Tumor (more common) |
| United Kingdom | Tumour |
| Australia | Tumour |
| New Zealand | Tumour |
| Ireland | Tumour |
Medical organizations usually follow the spelling standard used in their own country.
Tumour or Tumor Comparison Table
| Feature | Tumour | Tumor |
|---|---|---|
| Correct spelling | Yes | Yes |
| American English | No | Yes |
| British English | Yes | No |
| Meaning | Abnormal tissue growth | Abnormal tissue growth |
| Medical meaning | Same | Same |
| International usage | Common in Commonwealth countries | More common globally |
FAQS
Is tumour or tumor correct?
Both are correct. The spelling depends on whether you use British or American English.
Which spelling is used in the United States?
American English uses tumor.
Which spelling is used in the United Kingdom?
British English uses tumour.
Do tumour and tumor have different meanings?
No. Both refer to an abnormal growth of tissue.
Is tumor wrong in British English?
It is not technically wrong, but tumour is the preferred spelling in British English.
Which spelling should I use for medical writing?
Use the spelling required by your country, institution, or publication.
Can I use both spellings in one article?
No. Choose one spelling style and use it consistently throughout your writing.
Conclusion
Both tumour and tumor are correct spellings with the same medical meaning. The only difference is the English style you follow. Use tumor for American English and tumour for British English and many Commonwealth countries.
Always keep your spelling consistent so your writing looks professional and clear. If you want to learn more British and American spelling differences, read our guide on colour or color for another common example.
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