Sexual intercourse

Two or more persons enjoying sex with each other. Sexual intercourse is defined as any sexually insertive behavior using the penis, which means fucking a girl. It can be anal, oral or vaginal. Typically, when the phrase "sexual intercourse" is used, the common assumption is that a man inserted his penis into a woman's vagina.

If one person enjoys sex with himself or herself, it is called masturbation. Obviously, in this case there can be no sexual intercourse (except for that one guy I saw in a movie back in college)