Here are some examples of French words and phrases used by English speakers.
There are many words of French origin in English, such as croissant, baguette, déjà vu, naïve, police, role (or rôle), routine, machine, and hors d'œuvres, but this article covers only words and phrases that remain identifiably French. That said, the phrases are given as used in English, and may seem more French to English speakers than they do to French speakers. The general rule is that if the word or phrase looks better in italics, it has retained its French identity, but if it doesn't need italics, it has probably passed over into English.
Note that these phrases are pronounced using the French rules, and not the English ones. Thus, the stress most often falls on the final syllable, the final letter is silent (unless it's "r" or "à" or "é"), consequent words are pronounced without a pause between them, unaccented "e" is usually pronounced as , and final "n" is nasalized as /~/ (see International Phonetic Alphabet for English for a guide to phonetic symbols).
À bientôt! – see you later! (relatively uncommon in English)
Esprit de corps – lit. "spirit of the body", a feeling of solidarity among members of a group, morale.
L'esprit de l'escalier – thinking of the right comeback too late (lit. "staircase wit"), originally a witticism of Diderot, the French encyclopedist, in his Paradoxe sur le Comédien.
Fait accompli – something which happened and is unlikely to be reversed.
Faux amis – false friends (used to refer to words in two different languages that have the same etymology, but different meanings).
Moi – me, often used in English as an ironic reply to an accusation: "what, me?". Can sound pretentious if over-used in English, hence the joke "pretentious? moi?".
Né (when describing males) or née (when describing females) – born (past participle of naître – to be born), often used to give someone's former or maiden name.
N'est-ce pas? – isn't it? Used after a statement, as in "right?".
Tête-à-tête – lit. "head to head", a private meeting.
Tour de force – a masterly or brilliant stroke, creation, effect, or accomplishment (lit. "feat of skill" or "strength").
Vis-à-vis – lit. "face to face", in comparison with or in relation to.
Vive la différence – long live the difference, generally referring to difference between male and female.
Vive la France – long live France (often said with tongue-in-cheek sarcasm).
Voilà! or Et voilà! – there you go!
Zut alors! – "Shock!" or "Horror!"; a general exclamation
Seemingly French phrases used in English, but not in French
Auteur — in French it just means "author", but in English it means "film director who controls everything about the film, or other controller of an artistic situation". (Actually, the English connotation derives from French, or rather French film theory. Popularized in the journal Cahiers du cinéma, auteur theory maintains that directors like Hitchcock exert a level of creative control equivalent to the author of a literary work.)
Faux pas — in French it is a rarely used expression meaning 'to slip', literally 'false step', but in English it came to mean an embarrassing social error. The French would say gaffe.
Cause célèbre — an issue arousing widespread controversy or heated public debate.
Petard — as in "hoist by one's own petard", or caught in one's own trap. A petard is French for a banger - a small explosive device.
Double entendre (pronounced dubble ontondr' or dooble ontond)-- double meaning, for which the French say double sens. Interesting to note that, in French, entendre (= hear) first meant understand, a meaning now seldom found in usual practice.
Encore — extra song(s) played at the end of a gig, literally means "again" (French would say bis).
Le mot juste — the right word. (means the same literal thing in French, but isn't used in the particular context English-speakers use it).
Venue — location of an event, from venir, literally means "come" -- with a feminine ending -- (the past participle; not the infinitive).
French phrases in international air-sea rescue
International authorities have adopted a number of words and phrases from French for use by speakers of all languages in voice communications during air-sea rescues. Note that the "phonetic" versions are presented as shown and not in IPA.
SECURATE (securité, "safety") -- the following is a safety message or warning, the lowest level of danger.
PAN PAN (panne, "breakdown") -- the following is a message concerning a danger to a person or ship, the next level of danger.
MAYDAY (m'aidez, "help me") -- the following is a message of extreme urgency, the highest level of danger. MAYDAY replaced SOS in this function.
SEELONCE (silence, "silence") -- keep this channel clear for air-sea rescue communications.
SEELONCE FEE NEE (silence fini, "silence is over") -- this channel is now available again.
PRU DONCE (prudence, "prudence") -- silence partially lifted, channel may be used again for urgent non-distress communication.
MAY DEE CAL (médical, "medical") -- medical assistance needed.
It is a serious breach in most countries, and in international zones, to use any of these phrases without justification.
Communications Instructions, Distress and Rescue ProceduresCombined Communications-Electronics Board of Australia, Canada, New Zealand, United Kingdom, United States. PDF document.