What is the term used for a fertilized egg?

The term "zygote" refers specifically to the fertilized egg that results from the union of a sperm cell and an egg cell. This single cell marks the very beginning of a new organism's development. Following fertilization, the zygote undergoes a series of mitotic divisions and eventually forms an embryo, which then develops into a fetus if the organism is a mammal.

In contrast, a gamete denotes the reproductive cells—sperm and egg—that are involved in sexual reproduction, while an oocyte refers specifically to the female gamete before it has been fertilized. An embryo, on the other hand, is the term used after the zygote has begun to divide and develop into a multicellular organism. Understanding these terms and their specific roles in the reproductive process is crucial in biology, particularly in studies related to development and genetics.