My textbook states that
"If an engine is to do work on a sustained basis, the working substance must operate in a cycle; ie, the working substance must pass through a closed series of thermodynamic processes, called strokes, returning again and again to each state in every cycle."
I have not understood exactly why it is necessary for the heat engine to operate in a cycle. Why is the operation in a single direction less efficient than that in a cycle?
Please share your insights and help me. Much thanks in advance :-) Regards.
Edit: Although this question may, at first glance, come across as primitive and maybe even a little silly, I request you to please bear in mind that it has not been very long since I began my study of thermodynamics and also, I have only just graduated high school.