What is sex?
The question "what is sex" is more than a little complicated. In an episode of the great situation comedy Seinfeld, the titular character and his on-again-off-again girlfriend Elaine discuss when one can consider the act of sex to have taken place:
Elaine: Hey Jerry when do you consider that sex has taken place?
Jerry: I would say when the nipple makes its first appearance.
Seinfeld aside, one can logically suggest that sex is defined by the process in which two or more living beings stimulate each other through manipulation of genitalia. Because "sex" involves more acts between human beings than intercourse, in which the male and female genitals come into contact in such a way as to facilitate reproduction, and because it is difficult to deny that interplay involving the mouth of one individual and the genitalia of another constitutes sex, and because sexual activities occur between two or more males and/or two or more females, the suggestion that reproductive intent defines "sex" would be misleading. Sex is the act of physical and mental stimulation with the intention of achieving orgasm. That is about as close as this educator can come to defining "sex."
At first glance, the question, "What is sex?" seems straightforward. Many people may say that when a penis enters a vagina, this is sex. While this is true, vaginal intercourse is only one type of sex. It's important to remember that oral sex, anal penetration, and manual stimulation should also be included in the definition of sex.
That may leave some people to believe that the presence of an orgasm defines sex. While an orgasm can be an important part of intercourse, is not necessary in order for an act to be considered as sex.
Consent is another important piece of sex. Without it, the act should be considered rape instead.
With these things in mind, one must conclude that sex is the consensual act two or more people engaging in sexual stimulation with one another.