What is a catch 21?

Question

I know what a catch 22 is. What is a catch 21...?

Answer 1

It's actually a Catch-22, from the famous book by Joseph Heller.

"Catch-22 is a term, coined by Joseph Heller in his novel Catch-22, describing a general situation in which an individual has to accomplish two actions which are mutually dependent on the other action being completed first"

"The prototypical Catch-22, as formulated by Heller, considers the case of a U.S. Army Air Forces bombardier who wishes to be excused from combat flight duty. In order to be excused from such duty, he must submit an official medical diagnosis from his squadron's flight surgeon, demonstrating that he is unfit because he is insane. According to Army regulations, any sane person would naturally not want to fly combat missions because they are so dangerous. By requesting permission not to fly combat missions, on the grounds of insanity, the bombardier demonstrates that he is in fact sane and therefore is fit to fly. Conversely, any flyer who wished to fly on combat runs implicitly demonstrated that he was insane and was unfit to fly and ought to be excused, and to be excused this person would only need to submit a request. Naturally, such flyers never submitted such requests. Of course, if they did, the "catch" would assert itself, short-circuiting any such attempt to escape from combat duty."


There is no such thing as a catch-21

Answer 2

Catch 21 is being one short of a catch 22, which crzywrite answered perfectly.
(There is no such thing as a "Catch 21", unless it is some sort of card game I have never heard of.)

Answer 3

"
Catch 21 is used when you face a choice betwen 2 or more things, which both have drawbacks.
"

Best I could do...looks like it just comes from sloppy and mistaken use of the phrase "catch-22"

Answer 4

Don't you mean catch 22?