Southern Illinois University Edwardsville
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Published by: Instructional Services Department
Last Updated: August 22, 2005 
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1.  COMPOUND SENTENCES are separated by commas, but not compound elements:
            Compound sentence:  Mother left early, but Father stayed.
            Compound element: Mother and Father left the party early.

2.  ITEMS IN A SERIES are separated by commas.  It is now common to use a comma before the conjunction: Erma bought apples, pears, and oranges at the store.

3.  LONG INTRODUCTORY PHRASES OR CLAUSES that begin the sentence are followed by commas: At the crack of dawn, the enemy attacked. (phrase)
               When I play chess, I play to win. (clause)

4.  INTERRUPTERS (HOWEVER, IN FACT, ON THE OTHER HAND, NEVERTHELESS, etc.) are surrounded by commas: We knew, however, that our project would be difficult.

5.  APPOSITIVES (a word or phrase that follows a noun and renames it) are surrounded by commas: Henry Ford, a financial wizard, sensed the public's needs.

6.  ADDITIONAL INFORMATION about a noun that has clearly been identified is surrounded by commas:
            ADDITIONAL INFORMATION (USE COMMAS):
                        Jill, who was elected class president, is presiding at the next meeting. (additional)
            ESSENTIAL INFORMATION (NO COMMAS):
                        The student who was elected class president is presiding at the next meeting.
                                    (essential information to identify which student we are talking about)
Additional information is often called nonrestrictive, and essential information is called restrictive.

7.  ABSOLUTE PHRASES are separated from the sentence by commas since they have no grammatical function in the sentence.
            We returned to our homes, the game being over.
            Having returned to their homes, the residents celebrated.

8.  STATES and YEARS are separated from the rest of the sentence by commas:
            I traveled to Helena, Montana, last summer.
            September 11, 2001, is a date that I will always remember.   

9.  ADDRESSES use commas to separate the information (except between the state & ZIP code):
            Mark lives at 112 Main, Belleville, Illinois  62220.

10.  QUOTATIONS use commas:      
            She replied, "I do not care for your attitude."
            "Come in," she said.  "I've been expecting you." (2 sentences, so a period is used)
            "Come in," she said, "and join the group." (1 sentence)