Important terminology of IC engine

BORE(D)

The inside diameter of engine cylinder is known as bore. 
It is measured in mm.
In the bore piston is fitted.

PISTON AREA (A)::-

 The area of circle of diameter equal to the cylinder bore.

STROKE(L):-

When piston is in reciprocating motion, the distance travelled by the piston from one dead centre position to the other dead centre position

DEAD CENTERS:-

Extreme positions within which piston do its reciprocating motion.

1.TOP DEAD CENTER(TDC)-

Top most position of the piston towards the cover end side of the engine.

2.BOTTOM DEAD CENTER(BDC)-

Lower most position of the piston towards the crank end of the engine.

CRANK THROW/CRANK RADIUS:-

The distance between the center of the main shaft and center of the crank-pin is known as crank throw or crank radius.

SWEPT VOLUME(Vs):-

The volume of fluid that can be comprised within the top dead centers and the bottom dead centers.
Vs=A × L

CLEARANCE VOLUME(Vc):-

The volume that can be comprised within top dead center and the head of the cylinder.
Piston never enters this portion of cylinder.

TOTAL CYLINDER VOLUME(V):-

Sum of swept volume and clearance volume
Total cylinder volume = Vs + Vc

COMPRESSION RATIO(r):-

It is the ratio of total cylinder volume to the clearance volume.
r = Vs+Vc/Vc  
compression ratio of Petrol- 5:1 - 9:1
and for                     Diesel- 14:1 - 22:1