Bonsoir! can be considered formal or informal depending upon context. The greeting literally means "Good evening!" and tends to be more frequent in formal than in informal contexts. The pronunciation will be "bo-swar" in French.
it is an informal group
formal is the cinema and informal is a gay man
informal
It's both formal and informal. It depends on how you say it. If you say "Adiós, señora." it's formal. If you say "Adiós, amigo." it's informal.
formal and informal rhythm
what is formal and informal communication
formal
informal
There is no formal slang. Slang is informal language.
what is formal and informal shareholders agreement
Formal is polite, informal is rude and obnoxious.