Please allow me to pitch in my 2 cents. “Abuse” is any form of mistreatment which can be verbal, physical, mental and lastly sexual in nature. It depends on how it’s used in the context.
Sexual abuse is always associated with a certain degree of violence. On the other hand, a child may not necessarily be physically beaten in a child abuse case. They may be neglected or locked up in a house but nonetheless, it’s still abuse.