An oocyte is a female reproductive cell, also known as an egg cell. It is crucial for sexual reproduction, as it combines with a male sperm cell to form a fertilized egg, or zygote. Oocytes are produced in the ovaries and undergo a process called oogenesis, which involves several stages of development. In humans, females are born with a finite number of oocytes, which decrease in quantity and quality as they age. Each menstrual cycle typically results in the maturation of one oocyte, which is then released during ovulation. The health and viability of oocytes are important for fertility and successful pregnancy.