Merriam-Webster Collegiate Dictionary - theorem

 noun  Etymology: Late Latin ~a, from Greek theorema, from theorein to look at, from theoros spectator, from thea act of seeing — more at theater  Date: 1551  1. a formula, proposition, or statement in mathematics or logic deduced or to be deduced from other formulas or propositions  2. an idea accepted or proposed as a demonstrable truth often as a part of a general theory ; proposition the ~ that the best defense is offense  3. stencil  4. a painting produced especially on velvet by the use of stencils for each color  • ~atic adjective