French has a reputation for coldness that mostly comes from a single misunderstanding, and the misunderstanding is not about vocabulary.
It is about the door. In France you greet before you transact. Walk into a bakery and open with je voudrais une baguette, and you have skipped a step that is not optional. The reply will be correct and cool, and you will conclude that French people are unfriendly, and you will be wrong.
Say bonjour first, with a madame or monsieur attached, and the same person becomes a different person. This one habit outweighs every other item in this article.
The line most learners cannot see
bonjour: not a greeting so much as an entry fee. It opens shops, phone calls, lifts, waiting rooms and emails. Omitting it reads as treating a person as a machine.
tu / vous: the register spine of the language. Vous to anyone older, anyone professional, anyone you have just met, anyone behind a counter. Tu to friends, children, and colleagues who have offered it. The trap is not the first choice, it is the switch. Say on se tutoie ? and let them answer. Unilateral tu to someone who expected vous is the fastest way to sound presumptuous.
s'il te plaît: please, in its tu form, and s'il vous plaît in its vous form. These must agree with the pronoun you chose. Getting the pronoun right and the politeness formula wrong is a mismatch a French ear catches immediately.
Casual, but only with the right people
ouais: yeah. Perfectly normal with friends. In a meeting, with a client or answering someone senior, it reads as slouching. Oui costs nothing.
quoi: a casual tag dropped at the end of a sentence, roughly you know. Fine socially, out of place professionally.
Je m'en fous: I don't care, and it is stronger than the English. With friends it is unremarkable. Directed at a colleague's suggestion it is rude. The neutral versions are ça m'est égal or peu importe.
Ta gueule: shut up, and genuinely aggressive. It is not the casual version of anything. Between very close friends it can be joking; there is no situation in which a learner should reach for it.
The words that depend on latitude
putain: literally a coarse word, functionally an all-purpose exclamation. In Marseille and across the south it is close to punctuation and carries almost no charge. In a Paris office it is still swearing. Same word, genuinely different weight, and the geography is real rather than a stereotype.
con: in the north an insult, and not a light one, with conne for a woman. In the south, t'es con between friends is closer to you idiot said affectionately. Putain de con in Toulouse can be an expression of delight. This is the divergence most likely to mislead you in either direction.
bordel: a mess. Mild to moderate. C'est le bordel about a disorganised project is common in casual work speech and would not be in a formal report.
merde: about as strong as damn. Zut is the harmless version and sounds slightly childish, which is occasionally the effect you want.
What is not rude, only marked
du coup: so, therefore. Wildly overused by everyone under fifty and complained about by everyone over it. Not impolite. It just places you.
genre: like. Same category, same effect.
on: the ordinary spoken subject where a textbook uses nous, standard in every register including formal ones. On y va is not lazy. Nous y allons in casual speech is what sounds odd.
The apology that opens doors
The counterpart to bonjour is the softener before an imposition. Excusez-moi de vous déranger costs two seconds and changes the reception of whatever follows. So does je suis désolé used generously, and je vous en prie as a response to thanks.
French politeness is not more elaborate than English politeness. It is differently placed: front-loaded onto the opening of an interaction rather than distributed through it. Get the opening right and the rest is forgiving.
Where this sits alongside the rest
This is not the list of grammar and false-friend traps, which will catch you on meaning. And it is a French-specific version of the more general phase every learner passes through of sounding blunt by accident, where limited vocabulary strips out the softening you would apply in your own language.
How to learn where the line runs
Register cannot be looked up, because the same word sits on both sides of the line depending on who is in the room.
Save the room, not the word. Putain = swear word is nearly useless. Putain, said by the man at the market in Nîmes when the crate slipped, with no reaction from anyone is the actual information. Vokabulo Scenes are built for that, and a free account includes three.
Give Translate the whole exchange. A French sentence carries its register in its particles and its pronouns, not in its content words. The AI needs the sentence to see it.
Then watch the pronoun. For your first months, record whether each person said tu or vous to you. It is the single most useful field you can attach to a French contact, and it is the one thing no textbook can tell you in advance.
The short version
Say bonjour before anything else, every time, to everyone. Use vous until offered otherwise, and ask if you are unsure. Keep ouais for friends.
And when someone in Toulouse calls you con and smiles, they are being affectionate. Smile back.
Not sure whether what you just heard was friendly or not? Put the whole line into Vokabulo with who said it. Free to start on iPhone and iPad. 🇫🇷
