Two kinds of sentences are very close in appearance, but one needs a comma, and one does not. Here are some examples:
Morris parked the truck in the reserved space and wondered whether he would get a ticket.
Morris parked the truck in the reserved space, and he wondered whether he would get a ticket.
In the first sentence, no comma is required before the word and. This sentence has one subject, Morris, and two verbs, parked and wondered. Since Morris is the subject of both verbs, you do not put a comma before the second verb. If you did, that would be like putting a comma here: Morris, wondered whether he would get a ticket. There is a grammar rule that says you do not separate the subject from the verb. This kind of sentence has what is called a compound predicate: one subject with two verbs.
In the second sentence, there are two subjects and two verbs. Even though Morris and he are actually the same person, the word he counts as a separate subject. In effect, you are combining two entire sentences. When you combine two sentences, you need to clearly separate them. A comma is required before the word and to make the separation clear. This kind of sentence is called a compound sentence.
By the way, he did not get a ticket. My advice? Use a comma in a compound sentence, do not use a comma in a compound predicate, and do not park in the reserved space unless it is reserved for you.
About the Author:Jennie Ruby is a veteran IconLogic trainer and author with titles such as "Essentials of Access 2000" and "Editing with MS Word 2003 and Adobe Acrobat 7" to her credit. Jennie specializes in electronic editing. At the American Psychological Association, she was manager of electronic publishing and manager of technical editing and journal production. Jennie has an M.A. from George Washington University and is a Certified Technical Trainer (Chauncey Group). She is a publishing professional with 20 years of experience in writing, editing and desktop publishing.