theory
n. C / Un. an idea or set of rules that explains how something works or why something happens. It can be a proven scientific fact or just a guess you have about a situation.
n. a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained. In scientific contexts, it refers to a well-substantiated explanation, while in informal register, it often denotes a mere hypothesis or speculation.
The scientist developed a new theory about climate change.
In theory, the new software should save us hours of work, but we need to test it first.
While the general public often uses the term to describe a hunch, a scientific theory represents a framework supported by a vast body of evidence and rigorous testing.
From Middle French théorie, from Late Latin theōria, from Ancient Greek θεωρία (theōría, “contemplation, divine perspective, speculation, a looking at, a seeking”), from θεωρέω (theōréō, “I look at, view, see, consider, examine”), from θεωρός (theōrós, “spectator”), from θέα (théa, “view, perspective, sight”) + ὁράω (horáō, “I see, look”) [i. e. θέαν ὁράω (théan horáō, “see, look at a view; survey + genitive”)].
Often used with the preposition 'of' (e.g., 'theory of relativity') or 'that' (e.g., 'the theory that birds evolved from dinosaurs').
I have a theory about why he is late.I have a theory as to why he is late.While 'about' is common in casual speech, 'theory as to' or 'theory regarding' is preferred in formal academic writing.