Is it okay to use “unexpected” in the following way? Or should I use “an unexpectedly large number of….”?
An unexpected large number of people showed up.
"an unexpectedly large number of people" means that the number was unexpectedly large. In other words, some people were expected, but not so many. "an unexpected large number of people" means a large number of people, and those people were also unexpected.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
"an unexpectedly large number of people" means that the number was unexpectedly large. In other words, some people were expected, but not so many. "an unexpected large number of people" means a large number of people, and those people were also unexpected. There can be some overlap of meaning, but in your sentence (and indeed generally), the former would be a more common thing to say.