A "quadruplet" refers to a group of four offspring born at the same time from the same pregnancy. This term is commonly used in the context of human births, where a mother gives birth to four babies. Quadruplets can be either identical, sharing the same genetic material, or fraternal, each developing from separate eggs fertilized by different sperm. In addition to humans, the term "quadruplet" can also apply to other animals that give birth to four young at once. Quadruplets are relatively rare compared to single births or twins, making them a unique occurrence in both human and animal reproduction.