Domestic violence (also called battering) is any emotional, physical or sexual abuse by an "intimate partner". Intimate partners can be people who are married or not married; heterosexual, gay or lesbian; living together, separated or dating.
Domestic violence is a pattern of behavior, repeated over time, by which one partner controls and harasses the other through fear and the threat or use of violence. It rarely happens "just once", almost always getting worse over time. Without professional help, domestic violence will continue - even when the partner promises that it won't.