Definition of "decidable"

capable of being decided.  examples

(computer science) describing a set for which there exists an algorithm that will determine whether any element is or is not within the set in a finite amount of time.  examples

(logic) in intuitionistic logic, a proposition P is decidable in a given theory if it can be proven from the theory that "either P or not P", i.e. in symbols: P ∨ ¬ P .  examples