Decidable a. : Capable of being decided; determinable.

Example:
If L1 is Decidable and L2 is a subset of L1, is L2 recursively enumerable?

Taxonomy
theory, undecidable, formulas, Decidability, logical system, first-order theory, theorems, decidable set, validities, logic, equality, signature, first-order logic, first-order theories, first-order, consistent theory, free encyclopedia, Gödel's incompleteness theorems.

Defination from the web:
decidable refers to the existence of an effective method for determining membership in a set of formulas. Logical systems such as propositional logic are decidable if membership in their set of logically valid formulas (or theorems) can be effectively ...