Series

A Series is a longer and more extended format with a multiple group of programmes with the same set of characters which makes it a recognisable format. For example:

Holby City is a British medical drama television series that airs one a week BBC1. Holby City is a spin off from the medical drama Casualty, this therefore shows that Holby City and Casualty are partners in television programmes.
Holby City has a multiple group of programmes with the same st of characters which is a recognisable format, therefore making it a series.

http://www.youtube.com/watch?v=nlqsscWOfxM