For a language that can use finite number of steps (halt on all inputs in finite number of steps) to decide the membership, we call that decidable language. Also known as recursive language.

A language is decidable if its strings are [[computable set]]. In other words, there is a [[Turing machine]] called decider which accepts strings from the language and rejects all others, never ...

Abstract: A class of languages C is perfect if it is closed under Boolean operations and the emptiness problem is decidable. Perfect language classes are the basis for the automata-theoretic approach ...