The minimum legal age a person must have attained in order to legally give permission for sexual intercourse: statutory rape.
The age (often 18) at which a person can legally marry without obtaining consent from a parent or guardian; also the age (variable by state) at which a person can legally agree to have sexual intercourse. Someone who has sex with an under-age person—someone under the age of consent—is liable to a charge of statutory rape.
The age at which a minor may legally engage in voluntary sexual intercourse or no longer requires parental consent for marriage. It varies among states but is usually between ages 13 and 18.