[throttlebody]

Relays and contractors are the same. It's a coil physically movin some contacts together to allow current to flow. I got no idea why, where or how the naming came about or who decides. But i guess its the same as creeks and rivers, when does a creek become a river

[SAI_Peregrinus]

I'd say they're physically different, but logically the same. They're both a coil that moves some contacts to make or break a current path, but a contactor has physical differences which allow it to break much higher current. Contactors have features to ensure the arc resulting from breaking the connection can be extinguished, relays just assume no significant arc will form in the first place.

It's like the difference between a pickup truck with a ball hitch & a class 8 semi-truck with a fifth wheel coupling for a 53' trailer. Both are just vehicles that tow a trailer, but the physical details of how they do that are different in important ways.

[userbinator]

The term contactor came from industrial machinery, while relay came from telecoms.