Definition of a "Turn"

[Tantalus]

Sorry for this newbie question, but can anybody tell me exactly what is the defininition of 1 "Turn."

 

[Dell19]

A period of years where the decisions you have made are processed and the computer makes its moves. A turn can represent 1 to 50 years depending at what point of the game you are at.

 

[Smash]

in game options there is an option to wait at end of turn.Enable that and you will know.