Classification according to the working principle or structural characteristics of the relay:
1. Electromagnetic relay: An electrical relay that works by using the suction effect generated between the electromagnet core and the armature by the point in the input circuit.​​
2. Solid state relay: refers to a relay in which the input and output are isolated in which electronic components perform their functions without mechanical moving components.​​

3. Temperature relay: a relay that acts when the outside temperature reaches a given value.​​
4. Reed relay: a relay that uses a reed action sealed in the tube and has the dual functions of an electric shock reed and an armature magnetic circuit to open, close or switch circuits.
5. Time relay: When the input signal is added or removed, the output part needs to be delayed or limited to a specified time before closing or disconnecting its controlled circuit relay.​​
6. High Frequency Relays: Relays for switching high frequency, radio frequency lines with minimal loss.​​
7. Polarized relay: a relay that has a combined action of a polarized magnetic field and a control current through the magnetic field generated by the control coil. The direction of action of the relay depends on the direction of the current flowing in the control coil.​​
8. Other types of relays: such as photorelays, acoustic relays, thermal relays, instrumentation relays, Hall effect relays, differential relays, etc.