This article is from the Coffee and Caffeine FAQ, by Alex Lopez-Ortiz with numerous contributions by others.
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 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:
o 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.
o 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).
o 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.
o 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_.
o 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.
o 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.
o 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.
 
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