What is an oocyte?

An oocyte refers to an immature egg cell that is key in the processes of female gamete development and reproduction. During oogenesis, which is the formation of eggs, the oocyte undergoes several stages of maturation. The initial stage is the primary oocyte, which is arrested in prophase I of meiosis and will remain in this state until it is recruited for maturation during the menstrual cycle or other reproductive events.

As a female develops, the follicles containing oocytes mature, eventually leading to the release of a secondary oocyte during ovulation. The terminology is important to understand the differentiation stages of egg cells; the term "oocyte" specifically denotes that the cell has not yet matured into a fully developed egg or ovum ready for fertilization.

The other choices in the question reference concepts that are either related to male reproduction or specific components in the ovarian structure, and they do not pertain to the definition and understanding of an oocyte itself.