Size distribution is a research area that focuses on the study of the variation in size of particles or objects within a given sample or system. This can include analyzing the frequency of different sizes of particles, the range of sizes present, and the distribution patterns of sizes within the sample. Understanding size distribution is important in various fields such as environmental science, materials science, and biology, as it can provide valuable information about the physical and chemical properties of the sample or system being studied. Techniques used in studying size distribution include microscopy, spectroscopy, and particle sizing methods.