(algebra) A theorem which states that for each element of a given set that a given group acts on, there is a natural bijection between the orbit of that element and the cosets of the stabilizer subgroup with respect to that element.

(mathematics) An important statement about surfaces in differential geometry, connecting their geometry (in the sense of curvature) to their topology (in the sense of the Euler characteristic).

(computing theory) A fundamental theorem about the complexity of computable functions, stating that for any complexity measure there are computable functions that are not optimal with respect to that measure.

(mathematics) An important theorem on the existence and uniqueness of solutions to first-order equations with given initial conditions.

(mathematics) A basic result of complex manifold theory and complex algebraic geometry, describing general conditions under which sheaf cohomology groups with indices q > 0 are automatically zero.

(mathematics, physics) A theorem about certain vector spaces, relating to string theory.

(mathematics) The theorem that any closed, orientable, connected 3-manifold may be obtained by performing Dehn surgery on a framed link in the 3-sphere with ±1 surgery coefficients, and that each component of the link can be assumed to be unknotted.

(mathematics) A theorem stating that, given n measurable "objects" in n-dimensional Euclidean space, it is possible to divide all of them in half (with respect to their measure, i.e. volume) with a single (n−1)-dimensional hyperplane.

(mathematics) Any of various theorems that saliently concern mean values.

(calculus) A theorem that states for each value between the least upper bound and greatest lower bound of the image of a continuous function there is a corresponding point in its domain that the function maps to that value.