Word of the Day: idempotent

From Eric Lippert:

There are two closely related definitions for “idempotent. A value is “idempotent under function foo” if the result of doing foo to the value results in the value right back again.

A function is “idempotent” if the result of doing it twice (feeding the output of the first call into the second call) is exactly the same as the result of doing it once. (Or, in other words, every output of the function is idempotent under it.)