Top dead center (TDC) refers to the position of a piston in an internal combustion engine when it is at its highest point in the cylinder. This position is crucial because it marks the end of the compression stroke and the beginning of the power stroke. At TDC, the volume of the combustion chamber is at its minimum, allowing for maximum pressure when the fuel-air mixture is ignited. Understanding TDC is essential for various engine functions, including timing the ignition of the spark plug and the opening and closing of the valves. Accurate timing ensures optimal engine performance and efficiency, making TDC a key concept in automotive engineering.