The final, legal ending of a marriage, by Court order.
Marriage, once entered into, ends only by death of one of the spouses, or by the Government ending it, which power has been given to the Courts, the exercise of which is called a divorce.
Marriage is based on contract but contrary to other contract relationships, it cannot be broken merely by the consent of the parties.
The term divorce used to encompass most judicial processes which ended a marriage such as marriage annulment, or an order which suspended it (called divorce a mensa et thoro).
The Churches, up to 1857 in common law England, had the authority to annul a marriage or suspend its obligations as in divorce a mensa et thoro, but not to dissolve a marriage, something which could only be obtained through Parliament.
In 1857, England wheeled out a Matrimonial Causes Act, giving divorce jurisdiction to the judiciary: the Courts; such a serious matter that at first, the law required that the application be heard and determined by three judges.
REFERENCES:
Duhaime, Lloyd, Legal Definition of Adultery, Legal Definition of Marriage and Legal Definition of Cruelty.