Biocompatible refers to materials or substances that can safely interact with living tissue without causing harmful reactions, such as toxicity, inflammation, or rejection by the body. These materials are essential in medical devices, implants, and prosthetics, ensuring that they function effectively inside the human body without triggering immune responses or other adverse effects. Biocompatibility is a key consideration in the development of products like pacemakers, joint replacements, and dental implants, as it helps ensure patient safety and device longevity.