Sex may refer to either the gender of individuals in many species that are distinguished as being female or male. Constitutional law considers sex a "suspect classification", so classifications made by public entities based upon gender are strictly scrutinized for a compelling state interest to support it.
Sex may also refer to sexual intercourse. The definition of sexual intercourse varies by state. Various state and local laws regulate sex, such as laws criminalizing underage sex and prostitution, testing for sexually transmitted diseases, and sale of obscene material. For example, in Eureka, Nevada, a law was enacted making it illegal for men with moustaches to kiss women.
The following is one state's statutory definition of sex:
"(5) "Sexual intercourse" means any penetration of the female sex organ by the male sex organ."
