nisi

Taking effect at a specified date only if no cause is shown for modification during the interim.

Unless.

Unless; if not; — used mostly in law.

unless before; — a phrase applied to terms of court, held generally by a single judge, with a jury, for the trial of civil causes. The term originated in a legal fiction. An issue of fact being made up, it is, according to the English practice, appointed by the entry on the record, or written proceedings, to be tried by a jury from the county of which the proceedings are dated, at Westminster, unless before the day appointed (nisi prius) the judges shall have come to the county in question (which they always do) and there try the cause. See In banc, under Banc.

not final or absolute