A comma (,) usually indicates a pause between parts of a sentence. It is also used to separate items in a list. 

Rules for using commas

  1. Use a comma when a series of two or more adjectives modify a noun
    • Sal’s band plays loud, abrasive, complex music.
  2. Use a comma to separate three or more items in a series
    • Anna’s grandmother is good at making fudge, nursing hurt animals, tending fruit trees, telling stories, and playing Scrabble
  3. Use a comma before a coordinating conjunction (for, and, nor, but, or, yet, so) that joins two complete sentences 
    • Glenn was craving Krispy Kreme donuts, but he knew it was a bad idea to eat too much sugar before going to bed
  4. Use a comma after material that introduces a complete sentence
    There are six types of introductory clauses:
    • Dependent Word
      • Since my parents enjoy watching movies, they go every weekend.
    • Preposition
      • In Mexico, the Day of the Dead is a traditional holiday. 
    • Infinitive verb (“to” + verb)
      • To learn ballroom dancing correctly, you should take lessons. 
    • Past Participle
      • Walking home from school, the young boy found a fifty-dollar bill. (Present participle)
    • Signal Verb
      • Dr. King said, “At the center of non-violence stands the principle of love.” (Signal verb)
    • Transitional Word
      • Elaine caught the flu. Therefore, she had to miss her cousin’s wedding. (Transitional word)
  5. Use commas around a “nonessential clause” 
    A “nonessential clause” is material that is extra information and does not change the meaning of the sentence when taken out. 
    • My brother, who is single, lives in New York City. (nonessential)
    • My brother who is single lives in New York City. (essential)
  6. Use commas to set off information that “interrupts” the flow of a sentence
    Interrupters can be emotional interjections (oh, well, wow), parenthetical expressions (to be exact, in fact, it seems), and transitional words (moreover, however, therefore).
    • People think my English accent sounds fake. My girlfriend, however, thinks it’s attractive.