1550s, from Middle French théorème, from Late Latin theorema, from Greek theorema "spectacle, speculation," in Euclid "proposition to be proved," from theorein "to consider" (see theory).
theorem the·o·rem (thē'ər-əm, thēr'əm)n.
An idea that is demonstrably true or is assumed to be so.
A mathematical proposition that has been or is to be proved on the basis of explicit assumptions.
A statement in mathematics that is not a basic assumption, such as an axiom, but is deduced (see deduction) from basic assumptions.