Translation guide
The English word 'behaviour' covers a wide range of meanings, from general conduct to specific actions. In Japanese, the best translation depends on whether you're talking about someone's manners, natural actions, or scientific observations.
Describing how someone acts in terms of politeness, discipline, or social norms.
Refers to manners or conduct, especially in social settings. Often used with いい/悪い to mean good/bad behaviour.
He has good manners.
Teach children manners.
Attitude or demeanour. Often used for someone's outward behaviour or stance.
His behaviour is rude.
Conduct or behaviour, often used in formal contexts like school reports or police records.
Bad behaviour can lead to expulsion.
Describing what someone or something does, often in a neutral or observational way.
The most general word for behaviour or actions. Works for people, animals, and even systems.
I can't understand his behaviour.
Behaviour or conduct, often with a nuance of how one carries oneself. Slightly more formal than 行動.
Words and actions; behaviour in terms of what one says and does.
Describing how something functions or reacts under certain conditions, often in academic or technical contexts.
Behaviour of machines, systems, or physical phenomena. Common in engineering and science.
The behaviour of this program is strange.
Operation or behaviour, especially of machines or software.
Can also be used for systems or particles in physics, but 挙動 is more common.
行動 is the most general and neutral term for actions or behaviour. 振る舞い implies a more visible, often socially evaluated manner of acting. 行儀 specifically refers to manners and etiquette, often used for children or in formal settings.
If you want to say 'good behaviour' in the sense of politeness, use 行儀がいい, not 行動がいい. 行動がいい sounds like 'good actions' and is not natural for manners.
Observe animal behaviour.
彼の振る舞いは紳士的だ。
His behaviour is gentlemanly.
彼の言動には注意が必要だ。
We need to be careful about his behaviour (what he says and does).
Check the robot's behaviour.
量子の振る舞いは奇妙だ。
The behaviour of quantum particles is strange.