Missed or Misplaced Commas that Bomb your Paper
The following rules cover the most commonly missed applications of commas for older students. Commas needed for lists, dates, direct address, and other more basic uses are not included here. But these are the chief rules, slimmed down and simplified, that are usually the hardest to memorize and keep straight.
THE THREE COMMA RULES:
Use a comma when clauses and other “stuff” are —
3) or when joining two sentences with and-but-or-nor-for-so-yet.
1. Use a comma with most introductory elements
Use a comma after all introductory clauses, and after most other introductory ” stuff.” This stuff includes some introductory phrases (especially if they are long ones), and introductory-type words, such as: well, yes, however, therefore, & nevertheless.
Introductory Clauses (always get commas)
When we go to the ballgame, I want to buy a hotdog.
When I swim, I like to swim underwater.
(short but it’s an introductory clause so there’s no question. It gets the comma.)
Remember: ALL introductory clauses get a comma (and clauses have a subject+verb).
Introductory Phrases (if long)
On the bridge over the river in Shadydale, you might be attacked by a troll.
(long introductory phrase—actually three prepositional phrases strung together—so the comma helps)
Under the bridge you’ll find a troll.
(just a short introductory prepositional phrase, so you don’t have to put in a comma.)
You may take the road over the bridge. However, you’ll be attacked by a troll. (Introductory word “however” gets a comma)
Well, we might find a troll under that bridge. (introductory word “Well” gets comma)
Oh, I almost got clobbered by a troll. (introductory word “oh” gets comma)
2. Use a comma with non-essential elements.
Always use a comma with non-essential clauses, and often with other non-essential stuff. (“Non essential” just means it’s not necessary to the meaning of the sentence.)
Note: A non-essential clause usually has a parenthetical feel to it. In other words, the sentence would still make sense if you put the clause in parentheses.
The woman who is wearing the red hat is the one in charge.
This clause is essential because you don’t know which woman unless you know about her hat.
The woman in charge, who is the main speaker tonight, is a close friend of our family.
This clause is non-essential. You would know which woman is meant without it. Also, it sounds parenthetical like a side comment.
Appositives (renaming elements in a sentence)
My daughter Rebecca is a film buff.
“Rebecca” is an appositive renaming the subject “my daughter.” I have two daughters, and you won’t know which one unless I give you her name. Thus, her name is essential, so I do not put commas around it.
My son, Robert, likes to play the piano.
Now the name is non-essential because I have only one son, so it has to be him. The “Robert” is technically unnecessary and commas are appropriate.
[As you can see from these two examples, sometimes an author is showing the reader what is essential or not by the absence or presence of commas.]
John Williams, the famous composer, did the musical score for this film.
The name John Williams is enough for you to know who did the score. The fact that he is a famous composer is not essential to the essence of the sentence.
The famous composer John Williams did the score for this film.
There are lots of famous composers so you need the name John Williams to get the point. Thus, no commas.
3. Use a comma when joining two sentences (independent clauses) with “and, but, or, nor, for, so, yet.” Put the comma before the conjunction.
I’ll study my science this afternoon, and I’ll watch a movie with you tonight.
Two clauses make up the above sentence. Each one is independent and could stand alone. Just try dividing them up to check –
I’ll study my science this afternoon.
I’ll watch a movie with you tonight.
See? Each is fine by itself, so each is “independent.”
Now, don’t confuse a compound sentence with a sentence that simply has a compound verb. A compound sentence will have two subjects and two verbs –a verb for each subject. A compound verb is when you have only one subject and two or more verbs, as in:
I’ll study my science this afternoon and watch a movie with you tonight.
Now there’s only one subject doing two things, so this sentence has a compound verb (or compound predicate). It is no longer a compound sentence. No comma is needed.
There is an exception to this third rule about joining independent clauses (are there always exceptions?!)–When both the sentences are extremely short and clear, you may skip the comma:
Elizabeth laughed and Darcy smiled at her. – A comma might seem a bit intrusive here, but it wouldn’t be wrong.
Use a comma when clauses and other “stuff” are
3) or when joining 2 sentences with and-but-or-nor-for-so-yet.
And one final comment: if you memorize the rule as listed above, you will also now know the 7 words that join independent clauses (stand alone sentences). You can check for comma splices this way. A comma splice is when you mistakenly try to join two sentences with a word that is not an authorized co-coordinating conjunction. (Yes, there are folks who “authorize” such things!) Example:
Jane wanted to go to the basketball game, however, she found she had to babysit for her little sister instead.
However is not in your list of conjunctions, is it? So the above is a comma splice and is incorrect. You must either separate these sentences completely with a period, or keep them together using a semi-colon. A comma won’t work. It’s not kosher. No other words but and-but-or-nor-for-so-yet are coordinating conjunctions. So perhaps now that you have your list memorized, these other introductory words, such as however, won’t trip you up.