Series, in mathematics, sum of a sequence of terms (numbers or algebraic expressions). The terms in a sequence have a specific relationship and order based on how the terms are formed. The series may be finite (with a definite sum), or infinite. As more terms from an infinite series are added, the sum may approach a value called the limit. Series with a limit are said to converge; those without a limit diverge. Mathematicians have devised formulas and notations to express the values of a series and individual terms in a series.
See also: Mathematics.