Adjournment sine die (from the Latin "without day") means "without assigning a day for a further meeting or hearing". To adjourn an assembly sine die is to adjourn it for an indefinite period. A legislative body adjourns sine die when it adjourns without appointing a day on which to appear or assemble again.
It can be used in reference to United States legislatures whose terms or mandates are coming to an end, and it is anticipated that this particular body will not meet again in its present session, form, or membership. A legislative body adjourned in this way may be called back into special session, a reason why sine die adjournment rather than dissolution may be preferred in some cases.
A corporate board might adjourn sine die if the corporation were being sold, merged, or liquidated.
A convention or a series of mass meetings would adjourn sine die if the business of these meetings has been completed. In these cases, the adjournment dissolves the body.
A court may also adjourn a matter sine die, which means the matter is stayed until further notice. This may be due to various reasons. For example, if the case is started with a wrong procedure chosen, the judge may adjourn the matter sine die, so that the party may choose to start the action again with the correct procedure. It may also be thus adjourned if there is no possibility of proceeding in the foreseeable future—for example, an action may be adjourned sine die if the defendant is in prison and there is no prospect of continuing the action at that time. In a sine die adjournment of this type, the hearing stands open indefinitely, and could theoretically be resumed if the situation changed.
Adjournment sine die—as in "The One Hundred Tenth Congress of the United States closed its second session today by adjourning sine die"—is an adjournment until the next session of Congress, there usually being at least two sessions to each numbered Congress—e.g., the 110th Congress met in 2007 (first session) and in 2008 (second session). The next numbered Congress would have a different membership: Some members would not be running for election again, while others might not win reelection. Sine die adjournments in the Congress typically do not have a date certain, but rather are determined by the Speaker of the House and Majority Leader of the Senate at a later time.