Relay compatibility refers to the ability of a relay to function properly within a specific system or circuit. It involves several factors, including electrical, mechanical, and environmental conditions that must align with the relay’s specifications. When a relay is compatible with the system it is used in, it ensures that it will perform optimally without causing damage or malfunction in the larger system. Compatibility is not only about matching the electrical ratings of the relay with the system, but also ensuring the relay's physical size, mounting type, and communication protocols align with the system's requirements.