4 Stroke engine
n
nStroke is defined as the movement of the piston from the 'bottom dead center' (BDC) to the  'top dead center' (TDC) or the other way round, that is  from TDC to BDC. A four stroke engine has 4 strokes. 
n1º Intake.
n2º Compression
n3º Power
n4º Exhaust.