Diffuse, or spread, refers to the process by which particles, substances, or energy move from an area of higher concentration to an area of lower concentration. This natural tendency occurs in various contexts, such as the mixing of gases in the air or the dispersal of a drop of dye in water. In scientific terms, diffusion is driven by the random motion of molecules and continues until equilibrium is reached. This principle is essential in fields like biology, where it explains how nutrients and gases, such as oxygen and carbon dioxide, move across cell membranes.