The first stroke of the four-stroke cycle during which the piston moves downward from top dead center to bottom dead center creating a partial vacuum and sucking the fuel-air mixture into the cylinder.

One of the four 180-degree full "sweeps" of the piston moving in the cylinder of a four-stroke, internal-combustion engine (originally devised by Nikolaus Otto in 1876). During the intake stroke, the piston moves from TDC to BDC and inducts (draws in by lowering the pressure in the cylinder) air/fuel mixture through the induction system. Note: The 180-degree duration of the intake stroke is commonly shorter than the period during which the intake valve is open, sometimes referred to as the true "Intake Cycle." The intake stroke is followed by the compression stroke.

Same as Induction Stroke.