Entropy:Entropy is a measure of the disorder or randomness in a system. It increases as energy spreads out and becomes less concentrated.
Heat Death: Heat death refers to the theoretical end state of the universe where all energy is evenly distributed and no useful work can be done.
Carnot Efficiency: Carnot efficiency represents the maximum possible efficiency for an ideal heat engine operating between two temperatures. It depends only on the temperatures involved and not on the specific working substance used.