Summary
The comma is a punctuation mark that allows a pause and separation between clauses. It helps to clarify the relationships between ideas in a sentence.
How do I use them properly?
The comma is the most used and misused of all the punctuation marks. It is trickier than it might first appear, doing more than just indicating a pause in thought and rhythm. They give a sense of how pieces of a sentence fit together. Think about commas as flags that indicate a new, related idea is coming.
1. Separating independent clauses
Quick Use: Use a comma + a coordinating conjunction when separating independent clauses in one sentence.
Commas can be used to separate independent clauses, but with the addition of a coordinating conjunctions (and, but, for, or, nor, so, yet).
I warned Merrick about going alone, but he didn’t listen.
We paid entrance fees on arriving at the national park, and we received pamphlets given from a miserly hand.
Note: using a comma to separate the independent clauses without the coordinating conjunction produces what is known as a comma splice – a grammatical error.
2. Presenting subordinate clauses, phrases, and words (commonly adverbs and linking words) at the beginning of sentences
Quick Use: Put a comma after any introductory clause, phrase, or word that comes before the main clause. A general rule: if you can remove the phrase without making the sentence ungrammatical, then use a comma after it.
Any introductory clause, phrase, or word that comes before the main clause needs a comma.
Use commas to set off a subordinate clause that comes before the main clause:
After the summer break, I was excited to come back to my friends and my classes.
Use commas to set off any type of phrase that is not a part of the main clause:
The rain having gotten worse, we decided to abandon our yard work and seek shelter.
In 1453, Constantinople fell to the Ottoman Turks.
Use commas to set off an introductory word:
Thankfully, we didn’t get into that much trouble.
Moreover, she did not seem too enthusiastic about seeing the show.
3. Presenting modifiers in the middle of sentences
Quick Use: Use commas to enclose (one on either side) any modifiers put in the middle of a sentence to comment or give details on the essential meaning.
Use two commas, one at the beginning and one at the end, of a modifier (words, phrases, clauses that give extra meaning to a sentence that is, itself, not grammatically required). Think of commas functioning in this way as substitutes for parenthesis.
King Harald Hardrada, the last great Viking, had a coat of mail which he called “Emma.”
Milton’s reunion with his first wife Mary Powell was, from what was written in Edward Philips’ biography, a scene of supplication on Powell’s part.
4. Presenting subordinate clauses, participle phrases, and adverbs at the end of sentences
Quick Use: Add a comma before certain subordinate, participle phrases, and adverbs clauses that end a sentence (after the main clause).
Use a comma to set off subordinate clauses after the main clause:
He did it anyway, even though he knew that there would be dire consequences.
It is important to remember that commas are sometimes not needed in sentence-ending clauses. Generally, if and because clauses do not need commas, while even though and although clauses might (but not all the time – comma rules regarding subordinate clauses are the least standardized):
Perhaps people do evil because they subjectively think it’s right.
We went out to play football even though it was raining.
The best thing to do if you are confused about whether to add a comma or not to the modifier at the end of the sentence is to move it to the start. Introductory clauses, phrases, or words (adverbs) always need a comma after them, before moving into the main clause.
Use a comma before an adverb (a modifier-word ending in -ly) after a main clause:
We lost the compass, unfortunately.
Use a comma to set off participle phrases that follow a main clause:
‘Where does the sun fall to the earth?’ the child wondered, staring out at the sunset.
Note that a comma is only needed if the subject of the participle phrase is far in front of the phrase. If the subject is right next to the participle phrase, there is no need for a comma:
He looked up at the girl sitting in the tree, swinging her legs from a branch.
5. Quotations
Quick Use: Put a comma after verbs of speaking that set off direct quotations.
Use commas before direct quotations, before verbs of speaking:
Douglas McArthur declared, “I shall return.”
If you don’t use a verb of speaking to quote and include instead the quotation as a part of the sentence itself, there is no need for a comma:
Virgil declares he will “sing of arms and a man.”
