What does entropy measure in a physical system?

Entropy is a fundamental concept in thermodynamics and statistical mechanics that quantifies the level of disorder or randomness in a physical system. It reflects the number of possible arrangements or microstates that a system can have while still maintaining the same macroscopic properties such as energy and volume.

When a system has high entropy, it has a greater number of microstates available, leading to a state of higher disorder. Conversely, a system with low entropy is more ordered, with fewer possible arrangements of its components. This notion is crucial when understanding processes such as the Second Law of Thermodynamics, which states that in any energy transfer, the total entropy of an isolated system will tend to increase over time, illustrating a natural tendency toward increased disorder.

In a nutshell, the degree of disorder or randomness in the system is encapsulated in the concept of entropy, making it the correct answer.