Don't worry about the semantics.
A relay is an electrically operated actuator switch*.
A CONTACTOR is just a heavy-duty RELAY that can handle the high power required to drive an electric motor
* There are two basic types of RELAY actuator:
- the direct-acting SOLENOID, in which a moving core
or plunger is drawn into a coil when current
flows;- and the simple RELAY, in which a hinged plate is pulled against the end of the coil.