Q: My dictionary defines “raison d’être” as “reason for being,” but I frequently see it used as a substitute for “reason.” Is this ever correct?
A: We don’t know of any standard dictionary or usage manual that considers “raison d’être” a synonym for “reason.”
But as you’ve noticed some people do treat it that way, a usage that Henry W. Fowler criticized as far back as 1926 in the first edition of A Dictionary of Modern English Usage. To show “how not to use” the expression, he cites an example in which it means merely a reason: “the raison d’être is obvious.”
Oxford Dictionaries Online, one of the nine standard dictionaries we’ve consulted, typically defines “raison d’être” as the “most important reason or purpose for someone or something’s existence,” and gives this example: “seeking to shock is the catwalk’s raison d’être.”
Some writers italicize “raison d’être,” but we (along with The Chicago Manual of Style, 17th ed.) see no reason to use italics for a term in standard English dictionaries. However, all the dictionaries we’ve seen spell it with a circumflex.
As for the pronunciation, listen to the pronouncer on the Merriam-Webster Online Dictionary.
The Oxford English Dictionary, an etymological dictionary based on historical evidence, says English borrowed “raison d’être” from French in the mid-19th century. The expression ultimately comes from the Latin ratiō (reason) and esse (to be).
The earliest citation in the OED is from a March 18, 1864, letter by the British philosopher John Stuart Mill: “Modes of speech which have a real raison d’être.” The latest example is from the October 1995 issue of the British soccer magazine FourFourTwo: “Players, managers and supporters—the people for whom football is their raison d’etre.”
Jeremy Butterfield, editor of the 2015 fourth edition of Fowler’s usage manual, notes that since “raison d’être” means a reason for being, not just a reason, “it does not make a great deal of sense to modify it with words such as main, primary, etc.,” as in this example: “The main raison d’être for the ‘new police’ was crime prevention by regular patrol.”