What is the term for an immature female sex cell in the process of developing into an oocyte?

The term for an immature female sex cell that is developing into an oocyte is "oogonia." In the context of female gametogenesis, oogonia are the initial stage of development, forming during embryonic development before entering meiosis and becoming primary oocytes. Oogonia undergo several mitotic divisions and eventually differentiate into primary oocytes, which are then arrested in prophase I of meiosis until ovulation occurs.

The terminology within this process is specific, and understanding the correct classification is crucial. Oocytes refer to the actual cells that have entered the first stage of meiosis, while the egg cell is a fully mature ovum that is capable of being fertilized. A follicle refers to the structure that surrounds the oocyte and supports its development, but it is not a term that applies directly to the immature cell itself. Thus, the correct designation for the immature cell in development is indeed oogonia.