When do you switch from 'vous' to 'tu'? I know that vous is the polite form and is used to address superiors, older people, people you have just met etc. But when speaking with someone who is around the same age and station as you, when do you switch from vous to tu? Must there be a verbal acknowledgement i.e. 'on peut tutoyer', or can it be switched seamlessly within conversation once you have known someone long enough? And if so, how long is 'long enough'? How would I tell someone much older than myself to use 'tu' with me, even though I will continue to address them as 'vous'? Also - is it rude to use 'tu' right away with someone you've just met, if they are around the same age as you? Or does it denote a casualness (and therefore more approachability etc)?