Diffuse, or spread, refers to the process by which particles, molecules, or substances move from an area of higher concentration to an area of lower concentration. This natural tendency occurs in gases, liquids, and even solids, allowing for the mixing of different substances. For example, when a drop of ink is added to water, it gradually spreads throughout the liquid until evenly distributed. In biological systems, diffusion is essential for processes like cell respiration and nutrient absorption. Cells rely on diffusion to take in necessary substances, such as oxygen, and remove waste products, ensuring proper functioning and maintaining homeostasis.