Theory of everything
A theory of everything (TOE) is a putative theory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...

 of theoretical physics
Theoretical physics
Theoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...

 that fully explains and links together all known physical phenomena, and predicts the outcome of any experiment that could be carried out in principle.

The theory of everything is also called the final theory. Many candidate theories of everything have been proposed by theoretical physicists during the twentieth century, but none have been confirmed experimentally.