Q: It bothers me when a form reads, “By signing this you are giving your express permission for us to use your information.” Shouldn’t that be “expressed permission”?
A: In contemporary English, one usually gives “express permission,” not “expressed permission.”
We’ve checked six standard dictionaries and not a single one includes the adjectival use of the past participle “expressed” in this sense. In fact, Garner’s Modern American Usage (3rd ed.) describes it as a misuse that’s “widely shunned.”
All six dictionaries have entries for the adjective “express” used in transportation (“an express train”) and mail (“an express letter”), as well as the meaning you’re asking about and a related sense.
Oxford Dictionaries online, for example, includes these two adjectival senses:
(1) “Definitely stated, not merely implied: it was his express wish that the celebration continue.”
(2) “Precisely and specifically identified to the exclusion of anything else: the schools were founded for the express purpose of teaching deaf children.”
In your example (“By signing this you are giving your express permission for us to use your information”), the word “express” is being used in sense No. 1 to mean definite or explicit.
Although “expressed” is sometimes seen in this sense, “express” is overwhelmingly preferred, according to our online searches. Here’s the Google scorecard: “express permission,” more than 3.3 million hits; “expressed permission,” 356,000.
The Oxford English Dictionary (a historical dictionary that’s a separate entity from Oxford Dictionaries online) does indeed include the adjectival use of “expressed” to mean “express,” but its most recent citation is from the early 1700s.
When the adjective “express” showed up in written English in the 1300s (two centuries before the adjectival use of “expressed”), it meant explicit or definite, according to citations in the OED.
The dictionary’s first two examples are from The Wife of Bath’s Prologue in The Canterbury Tales (circa 1386). Here’s one of them:
“Wher can ye seen in any maner age / That highe God defended mariage / By expresse word?”
And this is a 1765 legal example from William Blackstone’s Commentaries on the Laws of England: “Express contracts are where the terms of the agreement are openly uttered and avowed at the time of the making.”
Finally, here’s an 1877 example from The American Commonwealth, by James Bryce: “Sometimes by express, more often by a tacit understanding.”
from Grammarphobia http://www.grammarphobia.com/blog/2016/03/express.html