Electrical

Google the terms and you're sure to find an answer.

Hint; one includes the other.

2 things generally separate the terms; application and size, and even those are nebulous.

As a gross generalization, we use the term Relay for devices rated under 30A and Contactors for over 30A. But there are contactors with smaller ratings, and there are relays with higher ratings.

So to further differentiate, a Relay is typically used to carry on or execute a command or amplify a signal, i.e. it is used in logic and/or transmission of information. A Contactor is usually the final device interface between the logic and a load that needs to be controlled by it, such as the device that switches a motor or heater element on and off.