a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena

(computer science) the technique of representing the real world by a computer program

a theoretical sun that moves along the celestial equator at a constant speed and completes its annual course in the same amount of time the real sun takes at variable speeds

(astronomy) Copernicus' astronomical model in which the Earth rotates around the sun

(astronomy) Ptolemy's model of the universe with the Earth at the center

(particle physics) a theory that involves an eleven-dimensional universe in which the weak and strong forces and gravity are unified and to which all the string theories belong