Entropy, in the thermodynamic sense, is the tendency of a system to move from a more ordered state to a less ordered state. In Boltzmann's statistical mechanics, the notion of "order" and "disorder", and thus the definition of entropy, corresponded to the number of possible microstates corresponding to a given macrostate. In information theory, Shannon entropy and Hartley entropy measure the distribution of discrete states in a system. A uniform distribution would have maximum entropy. Shannon entropy measures frequencies of states, while Hartley entropy ignores frequency and only examines the presence of states (out of all possible states).
- Information Theory, Entropy