In algebraic geometry, a period is a number that can be expressed as an integral of an algebraic function over an algebraic domain. Sums and products of periods remain periods, such that the periods form a ring.
Maxim Kontsevich and Don Zagier gave a survey of periods and introduced some conjectures about them.[1] Periods also arise in computing the integrals that arise from Feynman diagrams, and there has been intensive work trying to understand the connections.[2]