Murder is the highest form of culpable homicide...all culpable homicides are not necessarily murder...Culpable Homicide not Amounting to Murder is an offence under s.304 of the Indian Penal Code. It applies to an event where the death is intentional but does not come within the IPC definition of Murder... The difference between murder and culpable homicide not amounting to murder is very subtle. A great deal of caution has to be exercised in separating the two offences;

if death is the most likely result of an act, it will be murder.
if death is the likely result of an act, it will be culpable homicide not amounting to murder.
culpable homicide is a less serious offence than murder.