1. Top dead and Bottom dead Centre: These are 2 extreme positions between which the piston reciprocates inside the cylinder. TDC and BDC have relevance to opening and closing of valves and crank shaft rotation.
2. Bore: The inner diameter of cylinder is bore. In the automobile engines it varies from 40 - 120 mm.
3. Stroke: Displacement of the piston with in cylinder between TDC and BDC is called as stroke.
4. Swept Volume (Vs): Volume of the charge sucked into cylinder when piston travels from TDC to BDC during the suction stroke.
5. Clearance Volume (Vc): It is volume occupied by charge in space provided between TDC and end of cylinder.
6. Engine Capacity (VE): Capacity of engine can be defined as the sum of swept volume of all the cylinders.
7. Compression Ratio: The ratio of initial volume to the final compressed volume is called as compression ration. CR for petrol engine varies from 6.5 to12 where as for diesel engine it varies from 16to 23.