A provisional decision of a court which does not have force or effect until a certain condition is met such as another petition brought before the court or after the passage of a period time, after which it is called a decree absolute.
Although no longer required in many jurisdictions, this was the model for divorce procedures wherein a court would issue.
A decree nisi, which would have no force or effect until a period of time passed (30 days or 6 months).
This was designed to allow the spouses a mandatory, final cooling off period, a last-ditch encouragement at reconciliation before the ultimate severance occurred.
From the 1971 edition of Rayden on Divorce described:
"Every decree for divorce or for nullity of marriage is, in the first instance, a decree nisi, not to be made absolute until the expiration of three months from the pronouncing thereof unless the Court fixes a shorter time."
In the 2006 Oxford Dictionary of Law, the authors propose:
"Decree nisi: A conditional decree of divorce, nullity, or presumption of death.
"For most purposes the parties to the marriage are still married until the decree is made absolute. During the period between the decree nisi and the divorce absolute ... any member of the public may intervene to prevent the decree being made absolute and the decree (nisi) may be rescinded if obtained by fraud."
- Jackson, J. ed, Rayden's Law and Practice in Divorce and Family Matters, 11th Ed. (London: Butterworths, 1971) p. 568
- Martin, E. and Law, J., A Dictionary of Law, 6th Ed. (Oxford: University Press, 2006)