Can someone give me an example of an odd set. They were mentioned in an article i was reading but amazingly it didn't give an example!

Question

anonymous · Answer

i'll google - - why didnt i think about that before?  lol

anonymous · Answer

OK - i found it
an odd set is a set in which the set itself is an element of the set
an example is
'the set of all abstract ideas' - this is itself an abstract idea so its a member of the set.
Not sure if thats any practical use. Just academic.

I guess there cant be many of them.