theory

A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.

The branch of a science or art consisting of its explanatory statements, accepted principles, and methods of analysis, as opposed to practice.

A set of theorems that constitute a systematic view of a branch of mathematics.

Abstract reasoning; speculation.

A belief or principle that guides action or assists comprehension or judgment.