What does a decrease in the number of microstates indicate about a system's entropy?

A decrease in the number of microstates signifies a decrease in entropy for a system. Entropy is a measure of the number of ways a system can be arranged, which is directly related to its microstates—the different microscopic configurations that correspond to the same macroscopic state. When the number of microstates decreases, it implies that there are fewer configurations available for the system to occupy, leading to a more ordered state. This reduced disorder corresponds to a lower entropy value.

In thermodynamics, higher entropy is associated with a greater number of available microstates. This relationship highlights the connection between macroscopic properties of matter and microscopic behaviors at the molecular level. Therefore, when a system reflects fewer microstates, the overall randomness and degree of disorder diminish, resulting in lower entropy.