The definition of a scientific theory (often contracted to theory for the sake of brevity) as used in the disciplines of science is significantly different from the common vernacular usage of the word theory. In everyday speech, theory can imply that something is an unsubstantiated and speculative guess, the opposite of its meaning in science. These different usages are comparable to the opposing usages of "prediction" in science versus common speech, where it denotes a mere hope.
