Regeneration is the process by which an organism regrows lost or damaged body parts. This process can occur in both plants and animals.
Multiple fission, on the other hand, is a type of asexual reproduction that occurs in certain single-celled organisms, such as protozoa and some algae. During multiple fission, the organism's cell divides multiple times, resulting in the formation of many identical daughter cells. It is also known as schizogony or schizony.
In summary, regeneration is the process of regrowing lost or damaged body parts, while multiple fission is a type of asexual reproduction in which a single cell divides multiple times to produce many identical daughter cells.