What is a Cycle?

A cycle refers to the type of an engine either being a two cycle or a four cycle. One way to think of it is the up and down strokes of a piston. On a two cycle or stroke engine the air fuel intake and compression occur on the up stroke of the piston whereas the power and exhaust occur on the down stroke of the piston. On a four cycle or stroke, the intake, compression, power and exhaust happens as the piston goes up and down twice.