A motor vehicle's engine capacity is expressed in CC, though traditionally it is measured by horse-power. What does CC indicate?

The abbreviation stands for cubic centimetres, but it's not so simple as 'the volume taken up by the engine.' Cubic centimetres, as applied to motorcycle engine or automobile engine, is a measure of the combustion space in the cylin-ders. A typical engine works in four strokes of the piston in the cylinder: 

1. The intake stroke: The piston moves down, sucking the fuel-air mixture into the cylinder. 
2. The com-pression stroke: The piston goes up to compress the fuel-air mixture into a small space. 
3. The power stroke: The fuel-air mixture explodes, pushing the piston back down. 
4. The exhaust stroke: The piston returns to the top, pushing the exhausted gases out of the cylinder. 

All internal combustion engines work in this way, though some have a 2-stroke cycle instead of a 4-stroke one. The size of an engine is measured by theoretically removing the top of a cylinder, pushing the piston all the way down, and then filling the cylinder with liquid. The cubic centimetres of liquid displaced (spilled out) when the piston is returned to its high position is the measure of the com-bustion area of that cylinder. If a car has four cylinders, each displacing 200 CCs, it has an 800 CC engine. It was for this reason Maruti Udyog's first car was known as Maruti-800.