Here’s a spelling question that divides the English-speaking world as cleanly as a fence down the middle of a yard. Behaviour vs behavior, one is correct in London, Sydney, and Toronto. The other is correct in New York, Chicago, and Los Angeles. Both are right. Neither is wrong. The only mistake is using the wrong one for your audience.
This guide covers everything: the full definition, the etymology behind both spellings, which countries use which form, what major style guides say, and how to handle every derived form correctly.
The One-Line Answer (Then the Full Picture)
“Behavior” is correct in American English. “Behaviour” is correct in British and Commonwealth English. Same word, same meaning, different regional spelling conventions.
| Form | Correct? | Dominant Region | Use It? |
|---|---|---|---|
| Behavior | Yes | American English | For US audiences and publications |
| Behaviour | Yes | British, Australian, Canadian, South African English | For Commonwealth audiences |
| Behavoir | No | Nowhere | Never (common misspelling) |
| Behavour | No | Nowhere | Never (common misspelling) |
The behavior or behaviour question isn’t about which is better. It’s about which fits your reader’s world.
What “Behavior/Behaviour” Actually Means: The Full Definition
Before diving into the regional split, it helps to understand how widely this word actually stretches across different fields. Most people think of it as a word about human conduct. It goes much further than that.
| Field | Definition | Example |
|---|---|---|
| Psychology | Observable actions and mental responses | “The study examined aggressive behavior in children.” |
| Biology | Organism responses to environmental stimuli | “Migration behavior in birds is seasonal.” |
| Computing | How software responds to specific inputs | “Undefined behavior can cause system crashes.” |
| Education | Student conduct and classroom actions | “The behavior policy outlined consequences clearly.” |
| Social science | Patterns of human action and interaction | “Consumer behavior drives market trends.” |
| Everyday usage | General conduct or manners | “Her behavior at the dinner impressed everyone.” |
In computing, “behavior” (with the American spelling) dominates internationally because American companies built much of the world’s foundational software infrastructure. Even British and Australian developers frequently write “behavior” in their code documentation simply because programming languages, frameworks, and technical standards originate primarily from the United States.
Etymology: Where the Word Came From and Why Two Spellings Exist
Understanding the history makes the behaviour or behavior question genuinely interesting rather than just a style issue.
The word traces back through Middle English “behavour” (recorded in the 15th century) to the Old French “avoir” and Latin “habere” meaning to have or hold. The “-our” ending arrived in English directly from French influence during the Norman period.
For centuries, both forms of English used the “-our” ending. Then came Noah Webster.
In 1828, Webster published A Dictionary of the American Language, a deliberate project to distinguish American English from British English and simplify spellings he considered unnecessarily complex. Webster systematically targeted “-our” endings, replacing them with “-or” throughout the dictionary. His rationale was essentially phonetic: if the “u” is silent, why include it?
| British Spelling | American Spelling | Webster’s Rationale |
|---|---|---|
| Behaviour | Behavior | Simplified “-our” to “-or” |
| Colour | Color | Removed silent “u” |
| Honour | Honor | Phonetic simplification |
| Favour | Favor | Consistent pattern |
| Labour | Labor | Systemic reform |
| Humour | Humor | Part of the same principle |
| Neighbour | Neighbor | Applied uniformly |
Webster’s dictionary became enormously influential in American education and publishing. Within decades, the “-or” spellings became the American standard. British English, with no equivalent standardization pressure, retained the original French-influenced forms.
“Spelling reform was one of Webster’s greatest contributions to American intellectual independence.” historian Henry Steele Commager
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“Behavior” in American English: Complete Usage Guide
In American English, “behavior” is the only accepted form. There are no exceptions, no informal variants, and no contexts where “behaviour” would be preferred over “behavior” for an American audience.
American English derived forms follow the same pattern:
| Base Word | Derived Form | Example |
|---|---|---|
| Behavior | Behavioral | “A behavioral analysis revealed clear patterns.” |
| Behavior | Behaviors | “Multiple behaviors were observed during the study.” |
| Behavior | Behaviorism | “Behaviorism focuses on observable actions.” |
| Behavior | Behaviorist | “The behaviorist conducted the experiment.” |
| Behavior | Behaviorally | “She was behaviorally consistent across settings.” |
| Behavior | Misbehavior | “Misbehavior in the classroom disrupted learning.” |
The American Psychological Association (APA), which produces the most widely used academic style guide in social sciences worldwide, uses behavior exclusively throughout its publications and the APA Publication Manual.
“Behaviour” in British and Commonwealth English: Complete Usage Guide
In British English, “behaviour” is the standard form and it extends throughout the entire Commonwealth. Understanding the Canadian spelling of behaviour is particularly useful because Canada sits geographically adjacent to the United States yet follows British spelling conventions for this word.
| Country/Region | Preferred Spelling | Exceptions |
|---|---|---|
| United Kingdom | Behaviour | None: “behaviour” always |
| Australia | Behaviour | Rare American influence in tech writing |
| Canada | Behaviour | Some American influence accepted |
| New Zealand | Behaviour | None: follows British standard |
| South Africa | Behaviour | None: follows British standard |
| India | Behaviour | None: follows British standard |
| Ireland | Behaviour | None: follows British standard |
| Singapore | Behaviour | None: follows British standard |
The Canadian spelling of behaviour is “behaviour” with the “u” preserved. Canadian English generally follows British spelling conventions despite American cultural influence, and behaviour is one of the clearest examples of that tendency. Most Canadian universities, government documents, and national publications use “behaviour” consistently.
British derived forms mirror the American ones in function but maintain the regional spelling:
| Base Word | Derived Form | Example |
|---|---|---|
| Behaviour | Behavioural | “A behavioural analysis revealed clear patterns.” |
| Behaviour | Behaviours | “Multiple behaviours were observed during the study.” |
| Behaviour | Behaviourism | “Behaviourism focuses on observable actions.” |
| Behaviour | Behaviourist | “The behaviourist conducted the experiment.” |
| Behaviour | Behaviourally | “She was behaviourally consistent across settings.” |
| Behaviour | Misbehaviour | “Misbehaviour in the classroom disrupted learning.” |
Behavior/Behaviour in Psychology: The Most Important Professional Context
Psychology is where behavior or behaviour spelling choices carry the most professional weight. Getting it wrong in a published paper signals unfamiliarity with the conventions of your target journal.
| Publication/Body | Spelling Used | Why |
|---|---|---|
| American Psychological Association (APA) | Behavior | American organization, American English |
| DSM-5 (Diagnostic and Statistical Manual) | Behavior | American Psychiatric Association publication |
| British Psychological Society | Behaviour | British organization, British English |
| Journal of Behavioral Medicine | Behavior | American publication |
| Behaviour Research and Therapy | Behaviour | British journal |
| Cognitive Behavioral Therapy (US) | Behavioral | American clinical terminology |
| Cognitive Behavioural Therapy (UK) | Behavioural | British clinical terminology |
B.F. Skinner, working at Harvard from the 1930s onward, built the foundational framework of behavioral psychology using American spelling throughout his work. Ivan Pavlov, working in Russia but translated into English, appears in American texts as establishing the science of “behavior.” The DSM-5, published in 2013 by the American Psychiatric Association, uses “behavior” throughout its 991 pages.
British clinical and research traditions use “behaviour” just as consistently. The journal Behaviour Research and Therapy, founded in 1963, has published thousands of peer-reviewed studies using the “-our” form throughout its entire history.
What Major Style Guides Say About Behavior vs Behaviour
This is the section that matters most for professional writers and it’s the section most competitors skip entirely.
| Style Guide | Spelling | Audience | Authority |
|---|---|---|---|
| AP Stylebook | Behavior | American journalism | American news media |
| Chicago Manual of Style | Behavior | American publishing | American books/academic |
| APA Publication Manual | Behavior | International psychology | Research and academic |
| Oxford Style Guide | Behaviour | British publishing | British books/academic |
| Guardian Style Guide | Behaviour | British journalism | British news media |
| The Economist Style Guide | Behaviour | International | Global English-language business |
The Economist, despite targeting a global readership, uses “behaviour” throughout because it’s a British publication. This is worth noting for writers creating international business content: The Economist’s style choice confirms that “behaviour” works perfectly well in global professional contexts.
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Common Spelling Mistakes Beyond the Regional Split
The behaviour vs behavior discussion usually focuses on the regional difference but several misspellings have nothing to do with regional preference and everything to do with finger errors:
| Incorrect Spelling | Correct Form (US) | Correct Form (UK) | Error Type |
|---|---|---|---|
| Behavoir | Behavior | Behaviour | Vowel transposition (o and i swapped) |
| Behavour | Behavior | Behaviour | Missing letter |
| Behaivor | Behavior | Behaviour | Vowel transposition |
| Behaviuor | Behavior | Behaviour | Letter insertion |
| Behavor | Behavior | Behaviour | Missing letter |
“Behavoir” is by far the most common misspelling. Writers typing quickly transpose the “o” and “i” and spell-checkers sometimes fail to catch it if the surrounding context is clear. Always proofread this word specifically in professional documents.
The Complete Word Family: Every Related Form You Need
| Form | American | British | Part of Speech |
|---|---|---|---|
| Base noun | Behavior | Behaviour | Noun |
| Plural | Behaviors | Behaviours | Noun |
| Adjective | Behavioral | Behavioural | Adjective |
| Adverb | Behaviorally | Behaviourally | Adverb |
| Movement | Behaviorism | Behaviourism | Noun |
| Practitioner | Behaviorist | Behaviourist | Noun |
| Negative | Misbehavior | Misbehaviour | Noun |
| Verb | Misbehave | Misbehave | Verb (no difference) |
One interesting exception: “misbehave” has no regional spelling difference. The verb form doesn’t carry the “-our” vs “-or” distinction because it’s built on “behave” rather than “behaviour/behavior.” Both American and British English writers spell it identically.
How to Decide Which Spelling to Use: The Complete Decision Guide
| Question | If Yes | Use |
|---|---|---|
| Are you writing for an American audience? | Yes | Behavior |
| Are you following AP or Chicago style? | Yes | Behavior |
| Are you writing for a British/Commonwealth audience? | Yes | Behaviour |
| Are you following Oxford or Guardian style? | Yes | Behaviour |
| Are you at an American university? | Yes | Behavior |
| Are you at a British/Australian university? | Yes | Behaviour |
| Are you writing tech or software documentation? | Yes | Behavior (US tech dominates) |
| Are you writing for an international audience without a style guide? | Yes | Either: pick one, stay consistent |
The last row deserves emphasis. When you’re writing for a genuinely international audience with no style guide specifying a preference, consistency matters more than which form you choose. Switching between “behavior” and “behaviour” within a single document signals editorial inattention regardless of which form you prefer.
Memory Tricks That Make the Choice Permanent
Three anchors that work immediately:
The “U” pattern: British English preserves “u” across an entire family of words: colour, honour, favour, labour, behaviour. If you’re writing for a British or Commonwealth audience, keep the “u” in all of them consistently.
The Noah Webster anchor: Webster removed the “u” in 1828 as part of American standardization. If you’re writing for an American audience, use the form Webster created: “behavior” without the “u.”
The audience shortcut: Before writing a single word, ask yourself where your primary reader lives. American reader? “Behavior.” Commonwealth reader? “Behaviour.” It genuinely is that simple once you stop thinking about which is “more correct” and start thinking about which serves your specific reader.
Frequently Asked Questions
Is “behavior” or “behaviour” correct?
Both are correct. “Behavior” is the American English spelling and “behaviour” is the British and Commonwealth English spelling. The choice depends entirely on your audience and regional context, not on grammar rules.
Why do the two spellings exist?
Noah Webster deliberately simplified American spelling in his 1828 dictionary, changing “-our” endings to “-or” throughout. British English retained the original French-influenced spellings. The two varieties have maintained their separate conventions ever since.
What’s the Canadian spelling of behaviour?
Canada uses “behaviour” with the “u” preserved, following British spelling conventions. Despite American cultural influence, most Canadian universities, government publications, and style guides use the British form.
Which spelling do psychology journals use?
American psychology journals including those published by the American Psychological Association use “behavior.” British psychology journals including Behaviour Research and Therapy use “behaviour.” Check your target journal’s author guidelines before submitting.
Can I use both spellings in the same document?
No. Mixing “behavior” and “behaviour” within a single document creates inconsistency that editors and careful readers will notice. Choose one form and apply it consistently throughout, including all derived forms like “behavioral/behavioural.”
What are the most common misspellings?
“Behavoir” (vowel transposition) is the most frequent error. “Behavour” (missing letter) and “behaivor” (vowel transposition in the American form) also appear regularly in professional writing.
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Conclusion
This spellings are completely correct. Both have centuries of history behind them. Both appear in respected dictionaries, published books, peer-reviewed journals, and official government documents across the world.
The behavior or behaviour choice isn’t a grammar question. It’s an audience question. American readers expect “behavior.” British, Australian, South African, New Zealand, Indian, and Canadian readers expect “behaviour.” International style guides like The Economist use “behaviour” while American guides like AP and Chicago use “behavior.”
Pick the form that matches your reader’s world. Apply it consistently to every derived form: behavioral/behavioural, behaviors/behaviours, misbehavior/misbehaviour. And if you’re writing for a genuinely global audience without a style guide to consult, choose either form deliberately and then never switch.
