Coordinating Conjunctions


Rule: Do NOT begin sentences with coordinating conjunctions:

  • and
  • but
  • or
  • nor
  • yet
  • for
  • so

Subordinate Conjunctions


Rule: A subordinate clause begins with a subordinate conjunction or a relative pronoun. It must contain both a subject and a verb. It does not form an independent sentence because it is an incomplete thought.

Subordinate conjunctions:
    • after
    • although
    • as
    • because
    • before
    • even
    • even if
    • even though
    • if
    • once
    • rather than
    • since
    • so that
    • than
    • that
    • though
    • unless
    • until
    • when
    • whenever
    • where
    • whereas
    • wherever
    • while
    • why
Relative pronouns:
  • that
  • who
  • whom
  • whose
  • which
  • where
  • when
  • why

Rule: It is acceptable to begin a sentence with a subordinate conjunction. Use commas after subordinate clauses that begin sentences

  • Correct Example: Because of the rigorous basic training, stay prepared by getting into shape before you enlist.
  • Incorrect Example: While you wait do not touch any other keys on your keyboard. (The sentence should have a comma after “wait.”)


Rule: Do NOT use a preceding comma with a subordinate clause at the end of a sentence unless it introduces a nonessential clause.


Exception: Use a preceding comma if “while” is used to mean “whereas,” or if you are showing contrast (with “whereas,” for example).


  • Correct Example: Create a long-term plan that fits seamlessly into your lifestyle when you want a weight-loss plan that keeps those pesky pounds off permanently.
  • Incorrect Example: You are considered for an interview, once you fill out an application.


  • Correct Example: The bigger grill is a better choice if you host outdoor parties, while the smaller one is ideal if you generally cook only for a small family. (“While” is used to mean “whereas” and shows a contrast, so the comma is necessary; when “while” is used to mean “at the same time,” no preceding comma is used.)
  • Incorrect Example: The museum’s history is rich with examples although some are more notable than others. (“Some are more notable than others” is not essential to the meaning of the sentence; it’s bonus information. Therefore, “although” should be preceded with a comma.)



Rule: Use commas to set off subordinate clauses that appear in the middle of a sentence (interrupting the main clause).

  • Correct Example: Fold the remaining blueberries into the batter, even if you think stirring is faster, to prevent smashing them.
  • Incorrect Example: The rivalry between the schools while fierce in more modern times started rather mildly over 100 years ago. ("While fierce in more modern times” should be offset with commas.)