It's been more than 30 years, but I remember it as if it were yesterday: Peering at a large handwritten sign posted on the inside of the glass door of a bank branch in Paris, I translated for my parents: "Due to a strike, this branch is 'exceptionally' closed."
My dismay at finding the bank unavailable was offset, somewhat, by grudging admiration of the French for having a single adverb – exceptionellement – to express what English would need a whole prepositional phrase to convey.
The summer of 1979 was not a great year to be touring Europe on American dollars. And when we got to France, we were caught up in a wave of labor unrest, including actions at banks and museums and a series of one-day rail strikes that brought new meaning to the expression "You can't get there from here."
The era of just putting a card into the slot and getting bank notes out, in whatever color, plus or minus some transaction fees, was not quite upon us. In the end, we dealt with our frank need for francs by decamping to a branch of a German bank across the street, which was unaffected by the strike.
But the neatness of that exceptionellement has stuck with me. And speaking of the German branch across the street: German also has an adverb that is, as far as I can tell, a perfect equivalent: ausnahmsweise, "in the manner of an exception."
In English, however, exceptionally has come to be so widely used as an all-purpose intensifier ("an exceptionally fine chef") that it's no longer available for use in the narrower original meaning.
Something similar has happened with extraordinary. It ought to mean simply "out of the ordinary," which, as a phrase and as a concept packs no particular emotional punch, to my ear at least. But it's picked up quite some heft as one of those multi-purpose adjectives we all use, especially when that first "a" gets swallowed up in the stressed "o" sound – "Did you see the way she behaved at the party? It was ex-TROR-dinary."
How else might we say exceptionellement in English? "On an exceptional basis?" "Just this once"? There's one-off ("a one-off expense"). But it's an adjective, not an adverb, and not really American English anyway. And although I know better, it always sounds as if it means somehow "not up to par."
There's one-time, which is also an adjective, not an adverb, and also risks confusion with onetime. The Monitor and other publications distinguish between onetime meaning "former" ("onetime friend") and one-time meaning "single instance," as in "a one-time candidate for the Senate."
Trivia point: English tends to form its adverbs with the particle "ly," which comes from a root meaning "body." When you say, "I'll certainly be there," you are saying you will be there with "a body that is certain."
Romance languages form their corresponding adverbs with a suffix that means "mind." When a Frenchman says certainement, he'll be there, he's telling you he'll be there with "a mind that is certain."
Something else that is certain is that during the holiday season, some dining or other establishment near you is likely to be closed. A sign may say, "Closed for a private event" or some such. But you and I, dear reader, will know it is "exceptionally" closed.