An opinion is a statement prepared by a judge or court that announces the decision after a case is tried.
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Opinions include a summary of the facts; applicable laws, and how they relate to the facts; rationale to support the decision; a judgement.
The Supreme Court's opinions go through several generations--or stages--of publication.
"On days that opinions are announced by the Court from the bench, the text of each opinion is made available immediately to the public and the press in a printed form called a "bench opinion." http://www.supremecourt.gov/opinions/info_opinions.aspx
"Several days after an opinion is announced by the Court, it is printed in a 6" x 9" self-cover pamphlet called a "slip opinion." Each slip opinion consists of the majority or plurality opinion, any concurring or dissenting opinions, and the syllabus. It may [also] contain corrections..." http://www.supremecourt.gov/opinions/info_opinions.aspx
"...Brown, soft-cover "advance pamphlets" that contain, in addition to the opinions themselves, all of the announcements, ½ tables, indexes, and other features that make up the U.S. Reports. The contents of two or three preliminary prints will eventually be combined into a single bound volume." http://www.supremecourt.gov/opinions/info_opinions.aspx
"The fourth and final generation of opinion publication is the casebound set of law books entitled United States Reports." http://www.supremecourt.gov/opinions/info_opinions.aspx