Definition of Series

A series is obtained by adding the terms in a sequence.

(i) 6 + 8 + 10 + 12 + 14 +. . .

(ii) -1 + (-5) + (-9) + (-13) + (-17) . . .

(iii) 8 + 11 + 17 +. . .+ 47

The series (i) and (ii) are examples of infinite series. The dots indicate the series continues indefinitely. An infinite series has an indefinite number of terms, so it is impossible to find the sum of the term. However, a finite series contains a definite number of terms.

The series (iii) is an example of a finite series because the last term is given i.e. 47. Thus, it is possible to find the sum of a finite series.