Sexual intercourse is a biological process in which a male's penis enters a female's vagina. This act is often associated with reproduction, as it can lead to the fertilization of an egg by a sperm. It can also serve as a means of expressing intimacy and affection between partners. During sexual intercourse, various physical and emotional responses occur, including increased heart rate and the release of hormones. It is important for individuals to engage in safe practices, such as using condoms, to reduce the risk of sexually transmitted infections (STIs) and unintended pregnancies.