Agglutination is a process where particles, such as bacteria or red blood cells, clump together in response to the presence of specific antibodies or antigens. This reaction is commonly used in laboratory tests to identify and quantify substances in blood, such as blood typing or detecting infections. The clumping occurs because antibodies bind to multiple antigens on the surface of particles, creating visible aggregates. Agglutination is an important mechanism in the immune response and has various applications in diagnostics and research.