Why is the ninth month called September?
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.