1. Now children, I want you all to be on your best behaviour when grandma arrives.
2. I'd just met his parents for the first time so I was on my best behaviour.
behave extremely well and be very polite on a particular occasion
الواصلة
be·have ex·treme·ly well and be ve·ry po·lite on a par·ti·cu·lar oc·ca·sion
التركية النطق
bîheyv îkstrimli wel ınd bi veri pılayt ôn ı pırtîkyılır ıkeyjın