There is now a legal definition that the Courts, police, Home Office and other professionals work with to define Domestic Abuse.
The definition is:
“any incident or pattern of incidents of controlling, coercive or threatening behaviour, violence or abuse between those aged 16 or over who are or have been intimate partners or family members  regardless of gender or sexuality.
This can encompass, but is not limited to, the following types of abuse:
Controlling behaviour is a range of acts designed to make a person subordinate and/or dependent by isolating them from sources of support, exploiting their resources and capacities for personal gain, depriving them of the means needed for independence, resistance and escape and regulating their everyday behaviour. Coercive behaviour is: an act or pattern of acts or assault, threats, humiliation and intimidation or other abuse that is used to harm, punish, or frighten their victim.”
 Family members are: mother, father, son, daughter, brother, sister & grandparents; directly-related, in-laws or step-family.