An unwanted physical or verbal sexual behaviour/advance is called sexual harassment. It can be done by a person who is in authority toward a subordinate (such as an employee or student) or even some random man who brushes against your body on a public transport.
Abuse can be of various kinds – physical, emotional, financial or sexual. In an abusive relationship, there is a lack of respect, trust and consideration. Abusive relationships can be hard to recognise. Sometimes people stay in abusive relationships for years without realising they are trapped in one.