(physics) A candidate unified theory of all physical forces and particles; a theory which suggests that subatomic particles are one-dimensional strings rather than zero-dimensional points. It also suggests that space-time can have up to nine dimensions, plus the dimension of time.

The branch of mathematics dealing with the algebraic structure of rings.

A theory developed by Terence McKenna that aims to describe "novelty" in the universe based on a combination of numerology and mathematics, and supposed fractal patterns in the I Ching.

(mathematics) The mathematical study of probability (the likelihood of occurrence of random events in order to predict the behavior of defined systems).

(physics) A supposed theory uniting all fundamental physical phenomena into a single framework.

(mathematics) The mathematical theory of sets. / (music) Musical set theory, a systematic approach to describing musical objects and their relationships.

(chemistry) An obsolete scientific theory of combustion.

(uncountable, mathematics) The branch of mathematics dealing with the properties of graphs (networks of vertices and edges).

Any theory attempting to explain the process by which individuals explain the causes of behaviour and events.

(ecology) The theory that mitochondria and chloroplasts, which are organelles of eukaryotic cells, originated as independent organisms.