A two-stroke, two-cycle, or two-cycle engine is a type of internal combustion engine which completes a power cycle in only one crankshaft revolution and with two strokes, or up and down movements, of the piston in comparison to a "four-stroke engine", which uses four strokes to do so. This is accomplished by the end of the combustion stroke and the beginning of the compression stroke happening simultaneously and performing the intake and exhaust (or scavenging) functions at the same time.

Two-stroke engine
Two-stroke engine
Two-stroke engine
Valve assembly for a two-stroke engine
Emissions of aldehydes and ketones from a two-stroke engine using ethanol and ethanol-blended gasoline as fuel.
Improving Urban Air Quality in South Asia by Reducing Emissions from Two-Stroke Engine Vehicles
Evaluation of the Effects of Ozone Oxidation on Redox-Cycling Activity of Two-Stroke Engine Exhaust Particles
Comparisons of computed and measured three-dimensional velocity fields in a motored two-stroke engine
Determination of two-stroke engine exhaust noise by the method of characteristics
Particle Emissions from a Small Two-Stroke Engine: Effects of Fuel, Lubricating Oil, and Exhaust Aftertreatment on Particle Characte...
The Achates Power Opposed-Piston Two-Stroke Engine: Performance and Emissions Results in a Medium-Duty Application
12.O.02 Measurement and reduction of particles emitted from a two-stroke engine
A new two-stroke engine with compressed-air assisted fuel injection for high efficiency low emissions applications