The 2-stroke engine (also called a two-cycle engine) is a type of internal combustion engine that completes a two-phase supply cycle (up and down) of the piston during a single revolution of the crankshaft. In a two-stroke engine, the end of the combustion stroke and the start of the compression stroke occur simultaneously, with the suction and exhaust functions occurring simultaneously. Compared to four-stroke engines, two-stroke engines have a significantly reduced number of moving parts and therefore can be more compact and significantly lighter.