By far, the most common spelling used throughout the world today is "espresso". This is a shortened form of the original Italian name for the drink "caffe espresso" (accent marks omitted). This spelling is considered to be the correct spelling by the vast majority of coffee consumers, vendors, retailers, and producers.
Some English language dictionaries also list "expresso" as a variant spelling. However, this does not mean the spelling is 'equally valid.' (see the post by Jesse Sheidlower included below)
It was pointed out during the great "espresso vs. expresso" debate (spring '94) that the Italian alphabet does not even contain the letter "X," which is incorrect.
Further, it was discovered that at least three dictionaries contained incorrect definitions of the word "espresso". The American Heritage Dictionary gave the following definition:
"A strong coffee brewed by forcing steam under pressure through darkly roasted, powdered coffee beans."
The Oxford English Dictionary said:
"Coffee brewed by forcing steam through powdered coffee beans"
The Webster New World Dictionary gives:
"coffee prepared in a special machine from finely ground coffee beans, through which steam under high pressure is forced."
All three of these are wrong. In fact, espresso is a strong coffee brewed by quickly forcing hot water through darkly roasted, finely-ground coffee beans.
(Some espresso makers do use steam, but only to force the hot water through the ground coffee. The steam NEVER touches the coffee. Many espresso makers use no steam at all. Instead, they use either a pump or a piston to quickly force hot water through the ground coffee.)
Once these errors and the origins of the word "espresso" had been pointed out, the argument "but expresso is in the dictionary" quickly began to crumble. The final death blow to this position came in a post by dictionary editor Jesse Sheidlower. This post is reproduced in its entirety below:
Jesse Sheidlower writes
I find this thread fascinating. I regret that it demonstrates an unfamiliarity with dictionaries and how to use them, but no matter. I believe that I am the only dictionary editor to participate in this discussion, so let me waste a bit more bandwidth addressing some of the points made so far, and introducing a few others:
- The OED, Second Edition, does include _espresso_ and _expresso_, the latter being a variant of the former. It correctly derives it from Italian _caffe espresso_. [Accents left off here.] Whoever claimed it derives the term from a would-be Italian _caffe expresso_ was in error.
- There _is_ an "x" in Latin and Italian.
Mike Oliver points out that there are two Italian alphabets, one (il tradizionale) with no w, x or y, and the other one with all the letters in the English alphabet. The latter seems to be the one currently in use. (Reference: Il grande dizionario Garzanti della lingua italiana, Garzanti Editore s.p.a, 1987).
- There are four major American dictionaries (published by Merriam Webster, Webster's New World, Random House, and American Heritage). The most recent edition of each gives _espresso_ as the main form, and _expresso_ as a variant only. The fact that _expresso_ is listed in the dictionary does not mean that it is equally common: the front matter for each dictionary explains this. The person who claimed that three dictionaries including OED give _expresso_ as "equally valid" was in error.
- Dictionaries, in general, do not dictate usage: they reflect the usage that exists in the language. If a dictionary says that _espresso_ is the main spelling, it means that in the experience of its editors (based on an examination of the language), _espresso_ is notably more common. It does not mean that the editors have a vendetta against _expresso_.
- To the linguist who rejects the authority of dictionaries: I agree that language is constantly changing; I'm sure that every dictionary editor in the country does as well. Dictionaries are outdated before they go to press. But I think they remain accurate to a large extent. Also, if you are going to disagree with the conclusions of a dictionary, you should be prepared to back yourself up. I can defend, with extensive written evidence, our decision to give _espresso_ as the preferred form.
- The spelling _espresso_ is the form used by the copy desks of the _New York Times,_ _Gourmet,_ _Bon Appetit,_ The _Wine Spectator,_ the _Wall St. Journal,_ the _L.A. Times,_ _Time,_ _Newsweek,_ and to my knowledge every other major or minor newspaper or magazine, general or food-related, in the English-speaking world. The fact that a handwritten menu on an Italian restaurant door spells it "expresso" is trivial by comparison.
- In sum: though both _espresso_ and _expresso_ are found, the former is by far the more common. It is also to be favored on immediate etymological evidence, since the Italian word from which it is directly borrowed is spelled _espresso_. The form _espresso_ is clearly preferred by all mainstream sources.