or coitus or copulation
Act in which the male reproductive organ enters the female reproductive tract (see
Various sexual activities (foreplay) lead to physiological changes that progress to orgasm (climax) and resolution (see sexual response ). If it is completed, semen passes from the male into the female's body. If conditions favour fertilization , a sperm joins with an egg , and pregnancy begins (see fertility ; reproduction ); contraception can prevent this. Intercourse with an unwilling female is rape . See also reproductive behaviour ; safe sex ; sexuality, human ; {{link=sexually transmitted disease">sexually transmitted disease .