DefinitionThe sum of the geometric sequence, that is, the terms of the series, is the geometric series It can be finite and it can be infinite all depending on the number of terms being summed. A formula exists for finding the sum of a finite geometric series, but the sum of an infinite geometric series only converges if the common ratio is between -1 and 1. Geometric series are also important in mathematics, economics, and the sciences for analyzing natural processes, financial functions, and signal processing.