Use a comma before and, but or another coordinating conjunction linking main clauses (39a). - Use a commas to set off most introductory elements (39b). - Use a comma or commas to set off nonessential elements (39c). - Use commas between items in a series (39d). - Use commas between two or more adjectives that equally modify the same word (39e). - Do not use a comma between subject and verb, verb and object, or preposition and object (39h.1). - Do not use a comma in most compound constructions (39h.2). - Do not use a comma after a conjunction (39h.3). - Do not use a comma around essential elements (39h.4). - Do not use a comma around a series (39h.5).