(game theory) A theorem about finite two-person games of perfect information in which the players move alternately and chance does not affect the decision-making process. It states that if the game cannot end in a draw, then one of the two players must have a winning strategy, i.e. force a win.

(economics) The idea that capital accumulation is equal to production minus consumption.

(algebraic geometry) A theorem stating that a normal algebraic variety with an action of a torus can be covered by torus-invariant affine open subsets.

(geometry) A theorem stating that if A, B, and C are distinct points on a circle where the line AC is a diameter, the angle ABC is a right angle.

(mathematics) A result in combinatorics, stating that every set of integers with positive natural density contains a k-term arithmetic progression for every k.

(mathematics) The two-dimensional counterpart of the ham sandwich theorem.

(physics) A theorem that relates the time derivative of the expectation values of the position and momentum operators x and p to the expectation value of the force F=-V'(x) on a massive particle moving in a scalar potential V(x).

(mathematics) In additive combinatorics, a central result that indicates the approximate structure of sets whose sumset is small. It roughly states that if |A+A|/|A| is small, then A can be contained in a small generalized arithmetic progression.

(geometry) A statement in Euclidean geometry that deals with the construction of a particular parallelogram (the Varignon parallelogram) from an arbitrary quadrilateral.

(mathematics) Any of a collection of theorems of finite group theory that give detailed information about the number of subgroups of fixed order that a given finite group contains.