D50 refers to the median diameter of particles in a sample, indicating the size at which 50% of the particles are smaller and 50% are larger. It is commonly used in fields like pharmaceuticals, environmental science, and material science to assess the distribution of particle sizes in a given material. In practical applications, D50 helps researchers and manufacturers understand how particle size affects properties such as solubility, reactivity, and flowability. This information is crucial for optimizing processes like drug formulation, air quality assessment, and the production of various materials.