A landmark decision, Brown v. Board of Education desegregated the public schools.If an appositive is nonrestrictive (most are), it should be set off by commas. But if an appositive is restrictive, no commas should appear. Study these examples:
John's brother Fred came to dinner (restrictive, John has more than one brother and the appositive Fred singles out which brother, no commas).The terms restrictive and nonrestrictive are elsewhere defined.
Susan's brother, Jack, came to dinner (nonrestrictive, Susan has just one brother, commas are mandatory).