What really is sex?

To everyone that says sex means penetration:

Sex is whatever you consider it to be. As a bisexual female, I am able to have sex with female partners. Obviously there is no penetration involved, but it is still sex.

I thought we had escaped the idea that sex only happens when a penis enters a vagina.

There are millions of homosexuals and bisexuals in the world who would ask you to think otherwise.

You do not need to change your beliefs that sex should be between a man and woman only. But please respect the decisions of those around you and do not make them feel inferior by telling them their idea of sex is wrong.