Theory (mathematical logic)
SET OF SENTENCES IN A FORMAL LANGUAGE
First-order theory; Theory (model theory); Logical theory; Theory (logic); Supertheory; Subtheory; Logic theory; Deductive theory; Subtheories
In mathematical logic, a theory (also called a formal theory) is a set of sentences in a formal language. In most scenarios, a deductive system is first understood from context, after which an element \phi\in T of a deductively closed theory T is then called a theorem of the theory.