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Assuming your question is about steady state and transient operation of an engine (answer for a motor may be difference). Then,
Steady state is defined as a condition where parameters are relatively remain steady and unchanging in time. In an engine, the mass flow from one component is the same as the mass flow in an adjoining component.
A transient state is defined as a condition where parameters such as flow rate, temperature and pressure can vary with time. An example of transient state is the acceleration and deceleration of a car engine. During those transient states, power, pressure and temperature gradients occur causing changes in the engine components.