Episode

An episode is a singular part of a story, radio or television program. Episodes often follow in an order. They are often 20 to 40 minutes long, and follow the same storyline.
Origin of the word.
"Episode" comes from the Greek word "epeisodion" which refers to the spoken words between two songs in a Greek tragedy. The word was first used in English in 1773 to mean an "outstanding incident, experience." By the 1930s, the word was used to refer to each broadcast of a radio program that was part of a series.