Particle size refers to the diameter or dimensions of individual particles in a material. It is an important characteristic in various fields, including pharmaceuticals, materials science, and environmental science. Smaller particles often have a larger surface area relative to their volume, which can affect their reactivity and behavior in different environments. Measuring particle size can be done using various techniques, such as sieve analysis, laser diffraction, or dynamic light scattering. The size distribution of particles can influence properties like flowability, solubility, and stability, making it a critical factor in product formulation and quality control.