Writing Tip of the Week: Commas before Conjunctions Joining Main Clauses

When you join two main clauses with a coordinating conjunction, use a comma before the conjunction.  Although the terminology in this comma rule may sound complicated, it is really quite simple.  A main clause (or independent clause) can stand alone as a complete sentence, whereas a subordinate clause (or dependent clause) cannot stand alone. The seven coordinating conjunctions are as follows:  for, and, nor, but, or, yet, and so. You can use the mnemonic device “FANBOYS” to remember them.

• The defendant provided his own billing system, and he also paid for his own bookkeeping services. (“and” joins two main clauses)
• The appellate court held that the noncompete agreement was void, but it remanded the case for further determination on the question of trade secrets. (“but” joins two main clauses)

While it may be tempting to add a comma every time you use a coordinating conjunction, the rule applies only when you are joining two main clauses with one of the FANBOYS conjunctions.  A sentence with a compound verb does not have two main clauses; thus, it does not take a comma even though it contains a coordinating conjunction. 

• The defendant provided his own billing system and paid for his own bookkeeping services. (dependent clause comes after “and,” so no comma)

Likewise, do not use a comma to join two main clauses without a coordinating conjunction.  In that case, use a semicolon.

• The defendant provided his own billing system; he also paid for his own bookkeeping services. (two main clauses but no FANBOYS)

For more information, see Anne Enquist & Laurel Currie Oates, Just Writing 211-13 (3d ed. 2009) and Laurel Currie Oates & Anne Enquist, The Legal Writing Handbook 652-53 (5th ed. 2010).