noun
the general or abstract principles of a body of fact; scientifically accepted general principle or body of principles offered to explain phenomena; the popular misconception is that "theory" means "guess," which in science is not the case; in science, theory means general principles supported by evidence and facts, usually quite a large and diverse number of facts/studies; In the general public, the meaning of "hypothesis" (guess) is often confused with the meaning of "theory" (fact).
For something to qualify as a theory usually requires a raft of research (the standard of evidence is much higher), not just one study. In addition, the validity of this research is increased when there are a mix of methods and traits (multitrait-multimethod (MTMM) matrix).