Which engine type utilizes a spark plug for combustion?

The spark ignition engine is characterized by its use of a spark plug to ignite the air-fuel mixture within the combustion chamber. In this type of engine, fuel is mixed with air and drawn into the cylinders, where it is compressed. Once the piston reaches the appropriate point in the cycle, the spark plug sends an electrical spark to ignite the compressed mixture, causing an explosion that forces the piston down and generates power.

This method of ignition contrasts with compression ignition engines, which rely on the heat generated from compressing the fuel-air mix to ignite the fuel. External combustion engines use fuel that is burned outside the engine to produce steam or gas that does the work, without utilizing a spark plug. Hybrid engines integrate both combustion and electric technologies but do not specifically denote a combustion method involving a spark plug. Thus, the defining characteristic of a spark ignition engine is its reliance on spark plugs for the ignition process.