The diffusion coefficient is a numerical value that quantifies how easily particles spread out in a medium, such as a gas or liquid. It is influenced by factors like temperature, pressure, and the nature of the substances involved. A higher diffusion coefficient indicates that particles move more quickly and spread out more readily. In scientific studies, the diffusion coefficient is essential for understanding processes like gas exchange in the lungs or the movement of dyes in water. It helps predict how substances will behave in different environments, which is crucial in fields like chemistry, biology, and engineering.