Misplacement of punctuation can not only damage your credibility, but it can also change your intended meaning, leaving your reader confused and unimpressed. Avoid the dreaded “comma-itis” and other comma problems and mistakes by following these simple grammar tips.
1. Use the comma to separate independent clauses joined by a conjunction. The coordinating conjunctions are but, and, so,for, nor, yet, and or. Place the comma before the conjunction.
I needed to talk to the boss, but she was in a meeting.
2. Do not use a comma if two phrases are connected by a coordinating conjunction.
A tall man in a gray suit and silver cowboy boots entered the office.
3. Do use a comma if three or more phrases and clauses are connected with a coordinating conjunction.
Leslie went up the hallway, through the copy room, up the back stairs, and into the conference room.
4. Use the comma to separate items in a list, placing a comma before the coordinating conjunction. Some style guides, however, omit the final comma that precedes the coordinating conjunction in a simple series of three or more items, phrases, or clauses.
I bought hot dogs, hamburgers, buns, ketchup and mustard for the barbeque.
5. Use the comma to separate adjectives describing the same noun, but do not place a comma between the last adjective and the noun it modifies.
Highly educated workers staffed the bright, clean office.
6. Use the comma with introductory elements.
Over in sector 12, 42 computers were on the blink.
7. Use the comma to set off the nonrestrictive element in a sentence.
I gave the approval letter to Jean, the woman with long hair, on the third floor.
8. Use the comma to set off conjunctive adverbs and adverbial phrases.
I went to the door to see him; he turned, however, and walked away. The Toledo office, on the other hand, is doing great.