(in AM, use behavior)
1) N-VAR: with supp People's or animals' behaviour is the way that they behave. You can refer to a typical and repeated way of behaving as a behaviour.

Make sure that good behaviour is rewarded.

...human sexual behaviour...

These eating patterns are a learned behavior.

2) N-UNCOUNT: also N in pl, with poss In science, the behaviour of something is the way that it behaves.

It will be many years before anyone can predict a hurricane's behavior with much accuracy.

3) PHRASE: v-link PHR If someone is on their best behaviour, they are trying very hard to behave well.

English dictionary. 2008.