During what primary reproductive event does fertilization take place?

Fertilization is defined as the fusion of a sperm cell from a male with an egg cell from a female, resulting in the formation of a zygote. This crucial event primarily occurs during copulation, which involves mating where sperm is deposited into the female reproductive tract. The timing of copulation typically coincides with the female's ovulation period, when the egg is released and available for fertilization.

While ovulation is critical as it marks the release of the egg and creates the opportunity for fertilization, it does not itself involve the actual fusion of sperm and egg. Implantation refers to the process where the fertilized egg attaches to the uterine lining, and gestation is the period of development after implantation until birth. Therefore, fertilization specifically occurs during copulation, making it the primary event in this process.