Aerial view of campus with Williamsport, the Susquehanna River and Bald Eagle Mountain as a backdrop

Guidelines for Use Of Commas

Commas in Compound Sentences

  1. When you have two complete sentences (that is, independent clauses) joined by a co-ordinating conjunction, you MUST use a comma before the conjunction or you will have a comma splice.
    • Ex: Sam left early for the movie, but he forgot to bring his wallet.
  2. Here's an easy formula to remember: SV , + conj. SV (Read as: Subject and Verb comma plus conjunction Subject and Verb.)
    • That forumla should help you to remember that you need to have a complete sentence on both sides of the conjunction when you use a comma.
  3. Co-ordinating conjunctions may be remembered with this acronym: FANBOYS (For, And, Nor, But, Or, Yet, So).

Items in a Series

  1. Use commas to separate items in a series.
    • Ex: They enjoy biking, skating, and swimming.
  2. Use a comma before the "and" for clarity.
    • Ex: They served strawberry, peach, raspberry, vanilla (,) and chocolate swirl ice cream. (4 or 5 flavors? -- the comma lets you know.)

Commas with Introductory Phrases and Parentheticals

(words and phrases that could be put in parentheses)

  1. Use commas after all introductory phrases and clauses.
    • Ex: By the way, I forgot to get precise directions.
    • Ex: Until the patient was rudely awakened, he was enjoying a good rest.
  2. Use commas to set off parentheticals from the rest of the sentence.
    • Ex: Instructors, on the other hand, receive a lower salary than other teachers.
    • Ex: He prefers, as a rule, to hear classical music rather than rock.

Commas with Non-Restrictive (Non-Essential) Clauses Only

  1. A non-restrictive clause is NOT essential to the meaning of the sentence.
    • Ex: Bill, who is a part-time student, enjoys carpentry work.
  2. A restrictive clause is one that is essential to the meaning of the sentence.
    • Ex: Pens that slowly leak ink can be very messy. (Pens that don't leak aren't messy.)
    • Here's another example:
      • Essential:The man who was wearing the red suit brought presents. (We need the information in the modifying phrase to identify which man.)
      • Non-essential:Santa Claus, who was wearing a red suit, brought presents. (Now the clause becomes unnecessary for identifying the person who brought the presents.)

Commas with Appositives (like non-restrictive clauses)

  1. Appositives are phrases which rename or describe a noun but are not essential to identify the noun. They are set off from the rest of the sentence by commas.
    • Ex: Tom Hogan, a humorous and charming man, impressed the audience.
    • Ex: Long movies, especially with complicated plots, usually put me to sleep.

Commas in Dates and Addresses

  1. Dates should be written with some commas after the day AND year.
    • Ex: We arrived on July 17, 1998, to begin our experiments.
  2. Addresses should be written with commas after the street name, town or city, AND state.
    • Ex: We lived at 41 Maple Drive, Woodland Heights, New York, before moving here.
    • Note: Commas after the year and state name are the ones most frequently forgotten.

Minor Uses of The Comma

  1. Use a comma when answering a question after Yes or No.
    • Ex: Yes, I will remember those rules.
  2. Use a comma when addressing someone by name.
    • Ex: Sam, where did you put my law books?
  3. Use a comma after interjections like ah, oh, etc.
    • Ex: Ah, these chocolates are delicious.
  4. Use a comma to contrast.
    • Ex: Harry, not Ray, was chosen to direct the program.