Meaning

noun a proposition deducible from basic postulates

noun an idea accepted as a demonstrable truth

originFrom Middle French théorème, from Late Latin theōrēma, from Ancient Greek θεώρημα (theṓrēma, “speculation, proposition to be proved”) (Euclid), from θεωρέω (theōréō, “to look at, view, consider, examine”), from θεωρός (theōrós, “spectator”), from θέα (théa, “a view”) + ὁράω (horáō, “to see, look”). See also theory, and theater.

Etymology from Wiktionary, CC BY-SA 3.0