Punctuation is one of the more logical and helpful aspects of grammar. Commas are used between independent clauses when they are joined by and, or, so, nor, for, but, or yet. If no coordinating conjunction is used to join independent clauses, then the comma is incorrect. The semicolon is rarely needed in crisp writing in criminal justice. One exception might be the writings of probation officers. Because these officers are attached to the courts, they are sometimes required or expected to follow legal style. The colon usually means that something will follow. It is a form of punctuation often overused in police communications. The most frequent use of the apostrophe is to show possession. It can also show that something has been omitted. Parentheses are sometimes used to set off nonrestrictive material, that is, words that interrupt sentences and may add accuracy but do not alter the main meaning, although they tend to de-emphasize whatever they enclose.