Behavior and behaviour both describe the way a person, animal, or system acts, especially in response to a situation. Behavior is the spelling used in American English, and behaviour is the British spelling. A teacher in London notes a pupil's behaviour, while a teacher in Chicago notes a student's behavior, and both are describing the same conduct.
The core difference
Behavior and behaviour are the same word for how someone or something acts; only the American versus British spelling differs.
- behavior — American spelling: The therapist studies behavior to understand anxiety triggers.
- behaviour — British spelling: The teacher kept a note of each pupil's behaviour.
How to tell them apart
Both spellings cover the same idea, from a person's conduct to odd behavior in a piece of software suggesting a bug. The word traces back to Middle English behavour, built from behave plus a suffix borrowed by analogy from the older word havour, itself from Old French avoir, meaning to have.
Because behavior/behaviour follows the familiar -or/-our pattern seen in color/colour and honor/honour, it is easy to mix the two when copying text between American and British sources, especially in technical writing about software or psychology. Stick to one spelling throughout a document, and remember that related words like behavioural (UK) and behavioral (US) follow the same split.
