Table of Contents
Quick Answer
The fastest way to know which spelling to use.
The difference between behavior and behaviour comes down entirely to geography.
If you are writing for an audience in the United States, the correct spelling is behavior. If you are writing for an audience in the United Kingdom, Australia, or New Zealand, the correct spelling is behaviour.
Both words refer to the exact same thing: the way in which a person, organism, or system acts or conducts itself. Neither spelling is grammatically incorrect, but using the wrong one for your target region can look out of place.
Behaviour vs Behavior at a Glance
A side-by-side breakdown of the key differences.
| Feature | Airplane (US) | Aeroplane (UK) |
|---|---|---|
| Standard Region | United States | United Kingdom |
| Spelling | B-E-H-A-V-I-O-R | B-E-H-A-V-I-O-U-R |
| Syllable Count | 3 (bee-HAYV-yer) | 3 (bee-HAYV-yer) |
| Origin | Americanized spelling | Latin via Old French |
| Meaning | Conduct or actions | Conduct or actions |
American English: Behavior
How the word is used in the United States.
In the United States, "behavior" is the universally accepted spelling. It is used by the American Psychological Association (APA), educational institutions, researchers, and everyday speakers. The spelling drops the "u" entirely, favoring a simpler, more phonetic ending that matches other Americanized words like "color" and "honor."
Industry Standard
American psychological and scientific authorities exclusively use "behavior" in their academic journals, diagnostic manuals, and research papers.
Media and Publishing
Major publications like The New York Times and The Wall Street Journal follow the "behavior" spelling.
British English: Behaviour
How the word is used in the United Kingdom.
In the United Kingdom, "behaviour" is the traditional and standard spelling. It retains the "u," honoring the word's Old French origins. While British media increasingly discusses psychological concepts, "behaviour" remains the standard spelling for both human conduct and scientific analysis.
Cultural Presence
The spelling is deeply embedded in British culture, frequently appearing in school reports, psychology textbooks, and discussions of social etiquette.
Modern Usage
Though "conduct" is a broader term, formal British writing relies on "behaviour" rather than the American adaptation.
What Do Both Words Mean?
The definition remains exactly the same.
Despite the spelling difference, both "behavior" and "behaviour" mean exactly the same thing. They refer to the way in which one acts or conducts oneself, especially toward others, or the response of an organism or system to a specific stimulus.
Core Definition
The actions, reactions, and conduct of an individual, organism, or system in response to internal or external stimuli.
Scientific Definition
In psychology and biology, it refers to the observable activity of a living creature or the functioning of a physical system.
American English Usage
How Americans naturally use the word today.
In the US, "behavior" is used in almost every context, from casual conversations about parenting to technical manuals for software. While the broader term "conduct" often applies in strict legal settings, "behavior" is universally applied to everyday actions and scientific observations.
Casual Conversation
"I was impressed by her good behavior during the long meeting."
Technical Writing
"The algorithm models the behavior of consumers during a recession."
Education and Parenting
"The teacher noted his disruptive behavior in the classroom."
Scientific Industry
"The study observed the foraging behavior of the ants."
British English Usage
How Britons naturally use the word today.
In the UK, "behaviour" holds its ground in education, science, and daily life. However, in modern, casual speech regarding wild or unpredictable actions, many Britons might use the word "antics" or simply refer to someone "playing up."
Literature and Media
"The politician's erratic behaviour was criticised by the press."
Everyday Conversation
"The children were on their best behaviour at the dinner table."
Animal Contexts
"The documentary explored the mating behaviour of the birds."
News and Journalism
"Anti-social behaviour orders were introduced to curb minor crimes."
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 "behavior." If you are writing a postcard from London to your friends back in Britain, use "behaviour."
Choose "Behavior" if:
You are writing for a US-based publisher, studying at an American school, or creating content primarily for an American audience.
Choose "Behaviour" 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 business and academic contexts.
In highly formal writing, the safest approach is to use the broader term "conduct" or "actions" for both varieties of English. "Conduct" is universally accepted and avoids regional spelling pitfalls entirely in professional or legal contexts.
Business Contracts
International corporate contracts often use "professional conduct" to prevent ambiguity between American and British stakeholders.
Academic Research
Scientific papers regarding psychology generally use the regional spelling of the publisher, though "response" or "activity" may be used as alternatives.
Pronunciation
The spelling change does not affect how the word is spoken.
Despite the spelling difference, the word is pronounced exactly the same in both American and British English. The "u" in the British spelling is silent.
| Word | IPA | Syllables |
|---|---|---|
| Airplane (US) | /bɪˈheɪvjər/ | 3 (bee-HAYV-yer) |
| Aeroplane (UK) | /bɪˈheɪvjə/ | 3 (bee-HAYV-yer) |
Because the British version adds a silent "u," speakers do not add any extra syllables. Both dialects pronounce the word with three beats, emphasizing the second syllable. In non-rhotic British English, the final "r" is often softened, but the syllable count and stress remain identical.
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 simply ends with "-or." The British version retains the "-our" suffix derived from the Old French word "bihaveour," matching other British spellings like "colour" and "favour."
Why Are the Spellings Different?
The history behind the transatlantic split.
1. The British Adoption
When the word developed in Middle English, it was influenced by Old French and Latin roots. The British retained the "-our" ending, matching the established spelling conventions of words borrowed from French at the time.
2. Noah Webster's Reform
In the early 1800s, American lexicographer Noah Webster wanted to create a distinctly American version of English. He believed spellings should be simpler, more phonetic, and free of unnecessary silent letters. He successfully dropped the "u" from several words, including "behavior," "color," and "honor."
3. The Scientific Standardization
As the field of psychology grew in the 20th century, the American Psychological Association (APA) solidified the simplified "behavior" spelling in their official publication manual, cementing it as the undisputed standard in US scientific writing.
Synonyms, Antonyms & Rhyming Words
Words related to, opposite of, and sounding like behavior/behaviour.
Synonyms (Similar Meaning)
Example Sentences
See how both words function in original sentences.
Here are 30 original sentences using the American spelling, "behavior."
- The teacher praised the student for his good behavior.
- The scientist studied the foraging behavior of the ants.
- His erratic behavior worried his friends and family.
- The software monitors user behavior to improve recommendations.
- Parents often struggle to manage toddler behavior.
- The dog's aggressive behavior required professional training.
- The report highlighted the risky behavior of Wall Street traders.
- Cognitive behavior therapy is an effective treatment for anxiety.
- The audience's behavior during the play was extremely respectful.
- The machine learning model predicts consumer behavior.
- She was fired due to her unprofessional behavior at the office party.
- The documentary explored the mating behavior of penguins.
- Our cat's strange behavior usually means she is hungry.
- The school has a strict code of behavior.
- Is his silence a sign of defensive behavior?
- The psychologist observed a change in the patient's behavior.
- Reward systems can positively reinforce good behavior in children.
- The police officer noted the suspect's nervous behavior.
- Market behavior is often influenced by global news.
- Her quiet behavior hides a sharp intellect.
- The app tracks your sleeping behavior over time.
- Delinquent behavior often stems from a lack of guidance.
- The behavior of the waves indicated an approaching storm.
- He had to apologize for his drunken behavior at the wedding.
- Voting behavior has shifted dramatically in the last decade.
- We need to understand the behavior of the virus to develop a vaccine.
- The boss praised the team's collaborative behavior.
- Can you explain this bizarre behavior?
- Social media algorithms are designed to exploit human behavior.
- The judge sentenced him to community service for his reckless behavior.
Here are 30 original sentences using the British spelling, "behaviour."
- The headmaster sent a letter home regarding the boy's poor behaviour.
- The biologist documented the nesting behaviour of the seabirds.
- Her irrational behaviour baffled the medical staff.
- The website tracks user behaviour to target advertisements.
- It is difficult to manage the behaviour of a large group of toddlers.
- The rescue dog displayed fearful behaviour around men.
- The article discussed the spending behaviour of the younger generation.
- Cognitive behavioural therapy is widely available on the NHS.
- The crowd's behaviour during the royal procession was exemplary.
- The new AI model simulates the behaviour of stock markets.
- He was dismissed from his position due to gross misconduct and inappropriate behaviour.
- The nature programme highlighted the hunting behaviour of the cheetah.
- The horse's lame behaviour suggested it needed to see the vet.
- Pupils are expected to adhere to the school's code of behaviour.
- Was his sudden generosity a sign of guilty behaviour?
- The therapist noted a marked improvement in the client's behaviour.
- Sticker charts are often used to encourage good behaviour in primary schools.
- The constable observed the suspect's furtive behaviour in the alleyway.
- Consumer behaviour tends to slow down during economic uncertainty.
- His polite behaviour endeared him to the older relatives.
- The smartwatch monitors your heart rate and sleep behaviour.
- The council implemented new measures to tackle anti-social behaviour.
- The strange behaviour of the traffic lights caused a massive jam.
- She deeply regretted her behaviour at the office Christmas party.
- Electoral behaviour in the UK has shifted in recent years.
- Understanding the behaviour of the immune system is crucial for immunology.
- The manager commended the department's cooperative behaviour.
- How can we justify this reckless behaviour?
- Online platforms are often criticised for promoting addictive behaviour.
- The magistrate fined him for his disorderly behaviour outside the pub.
Behavior in US English
Specific contexts, industry standards, and cultural data for the American spelling.
In the United States, "behavior" is not just the linguistic standard; it is the scientific and psychological standard. American scientific regulators, academic institutions, and pop culture creators exclusively use this simplified spelling.
Legal & Regulatory Definition
The American Psychological Association (APA) defines it in their official glossaries:
"Behavior: The observable activity of an organism or system in response to internal or external stimuli."
Academic & Scientific Industry
American universities and research giants historically used "behavior" in all their academic charters, research grants, and technical manuals. Major US tech companies use the term in their data analytics.
Pop Culture & Media
The spelling is cemented in American pop culture through phrases like "behavioral economics," popularized by authors like Dan Ariely, and the hit reality TV show Bad Behavior.
Common American Phrases
• Good behavior: Acting politely or legally.
• Behavioral health: Mental health and substance abuse care.
• Animal behavior: The study of how animals act.
• On one's best behavior: Being exceptionally polite.
Behaviour in UK English
Specific contexts, industry standards, and cultural data for the British spelling.
In the UK, "behaviour" is the traditional, formal, and scientific standard. The British Psychological Society (BPS) and educational institutions use this spelling exclusively in their official documentation and curriculum.
Legal & Regulatory Usage
In UK law, the Anti-Social Behaviour Act explicitly uses the "-our" spelling. It is the standard term for conduct that causes harassment, alarm, or distress to the public.
Media & Publications
The UK has a strong tradition of science and education journalism. British magazines like The Psychologist and news outlets like the BBC consistently retain the "u" in their reporting.
Cultural & Literary Usage
The word appears frequently in British literature and historical texts. Early pioneers of psychology cemented the "-our" prefix in the national consciousness when discussing human behaviour.
Common British Phrases
• Anti-social behaviour: Disruptive public conduct.
• Behavioural science: The study of human actions.
• Code of behaviour: School or workplace rules.
• Bad behaviour: Mischievous or rude conduct.
Related Psychological Vocabulary
Other words that differ in the science and education industry.
| US English | UK English | Meaning |
|---|---|---|
| Behavioral | Behavioural | Relating to the study of actions. |
| Counselor | Counsellor | A professional who gives therapy. |
| Judgment | Judgement | The ability to make a decision. |
| Fulfill | Fulfil | To achieve or realize something. |
Other US–UK Spelling Differences
More words that change when you cross the pond.
Color vs. Colour
Americans spell it "color," while Britons spell it "colour," following the same dropped "u" pattern.
Labor vs. Labour
The word for work is "labor" in the US and "labour" in the UK.
Honor vs. Honour
The word for high respect is spelled "honor" in America and "honour" in Britain.
Humor vs. Humour
The word for comedy is spelled "humor" in the US and "humour" in the UK.
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 animal's behavior was strange behaviour" confuses the reader and breaks the consistency of your text.
Using "behaviour" in an American academic paper.
✓ Use "behavior" for US-based journals and schools.
Why: American professors and publishers expect standard American English, especially in strict APA formatting. Using the British spelling looks like a typo.
Hyphenating the word ("be-havior" or "be-haviour").
✓ Always use a single, unhyphenated word.
Why: Modern English treats both as solid compound words; hyphenation is incorrect in all contexts.
Using "behavior" for a British psychology journal.
✓ Use "behaviour" for UK audiences.
Why: British publishers strictly enforce regional spelling standards, especially in scientific and educational materials.
Mispronouncing "behaviour" as "be-hay-vee-or."
✓ Pronounce it "bee-HAYV-yer."
Why: The "u" in the British spelling is silent; it does not create an "oo" sound or add a distinct syllable at the end of the word.
Assuming "behaviour" is outdated or archaic.
✓ Recognize it as the current, active British spelling.
Why: Some Americans assume it's an old-fashioned word, but it is entirely modern and standard in the UK today, used by scientists and the public alike.
Misspelling derivatives like "behavioral."
✓ Adjust derivatives based on region (behavioral/behavioural).
Why: In the US, the adjective is "behavioral." In the UK, it is "behavioural." The spelling rule carries over to all forms of the word.
Translating "behavioral health" to "behavioural health."
✓ Check the region's specific medical terminology.
Why: While "behavioural health" is correct in the UK, the specific clinical phrasing might differ. Be aware of medical terminology variances.
Forgetting that Canada usually aligns with the US.
✓ Use "behavior" for Canadian academic audiences.
Why: Despite being in the Commonwealth, Canadian English heavily favors American spellings for words ending in "-or" vs "-our" in modern academic publishing.
Confusing the word with "conduction."
✓ Keep "behavior/behaviour" separate from "conduct."
Why: While they are synonyms, "conduct" is often used for strict moral or legal contexts, whereas behavior refers to the actual actions themselves.
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 scientific and educational organizations choose either US or UK English as their default and stick to it.
Pro Tip: Because the American Psychological Association (APA) style is globally dominant in academia, many ESL learners and researchers are more familiar with "behavior." However, if your organization is based in Europe or the Commonwealth, "behaviour" 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 letter "U." The United Kingdom has a "U" in its initials, and they keep the "U" in "behaviour." America drops the "U" for "behavior."
🎮 Mini Quiz
Test your knowledge with these interactive questions.
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Frequently Asked Questions
Quick answers to common questions.
Are 'behavior' and 'behaviour' pronounced the same way?
Yes, they are pronounced exactly the same. Both are pronounced with three syllables (bee-HAYV-yer). The 'u' at the end of the British spelling is completely silent.
Why does America use 'behavior' instead of 'behaviour'?
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 'behaviour' to create 'behavior' was part of this movement.
Is 'behaviour' ever used in the United States?
It is very rare in modern American English. You might occasionally see it in historical quotes or in the names of older British institutions, but 'behavior' is the undisputed standard, especially in scientific and academic writing.
What about Canada and Australia? Which spelling do they use?
Canada generally follows the American spelling ('behavior') in modern publications, though 'behaviour' appears in some older texts. Australia and New Zealand strictly follow British English and use 'behaviour'.
Do the spelling rules apply to derivatives like 'behavioral'?
Yes. In American English, it is spelled 'behavioral' (without the 'u'). In British English, it is spelled 'behavioural' (with the 'u'). The same applies to 'behaviorism/behaviourism' and 'behaviorist/behaviourist'.
Which spelling is older, 'behavior' or 'behaviour'?
'Behaviour' is the older spelling. It was adapted from the Old French word 'bihaveour'. 'Behavior' came later as an Americanized simplification.
Should I use 'behavior' or 'behaviour' 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 (especially if using APA style), use 'behavior'. For a British or Commonwealth journal, 'behaviour' is preferred.
What is 'cognitive behavioral therapy' (CBT)?
It is a common type of talk therapy. In the US, it is spelled 'cognitive behavioral therapy,' while in the UK, it is spelled 'cognitive behavioural therapy.' The acronym CBT is used globally.
Are there other words that follow this '-or' vs '-our' pattern?
Yes, many words follow this exact split, including 'color/colour', 'honor/honour', 'labor/labour', and 'flavor/flavour'.
Which word is more commonly used globally today?
Because of the dominance of the American Psychological Association (APA) and global scientific publishing, 'behavior' is highly recognized globally. However, 'behaviour' remains the correct standard spelling in formal British, Australian, and New Zealand English.
Quick Comparison
The final verdict on behaviour vs behavior.
| Factor | Airplane | Aeroplane |
|---|---|---|
| Region | USA | UK |
| Syllables | 3 | 3 |
| Safest Alternative | Conduct / Actions |
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