Virtually any unwelcome, unwanted, sexual touching of a child can be legitimately characterized as abuse. Physical injury does not have to be involved. As stated before, the child may seem to consent to the sexual contact, but a minor lacks the legal capacity to consent, rendering any sexual contact actionable. However, only on very rare occasions is consensual sex between two minors, such as two 16–year olds, the subject of any criminal prosecution.
Neither does sexual abuse always involve penetration between a penis and a vagina. Clearly, it is among the most reprehensible of examples. But, oral sex, fondling, and manipulation of the victim into any sexual acts by the abuser are actionable. Oftentimes, sexually tinged touching can become the focus of action. Sexual abuse of minors is not limited to acts perpetrated by males on females.
A good starting point to any analysis of what is abuse is, did the victim consent? “No” can be by “operation of law” (i.e. the minor lacks the capacity to consent), or an expressed rejection of any contact.
It is the exercise of power over an individual under circumstances that have an unwelcome sexual component that is the key to distinguishing sexual abuse or contact from innocent, welcome touching.