Commas and periods are the most frequently used punctuation marks in writing. Probably more commas are used than periods since a period is normally at the end of a sentence while a comma can occur several times in a sentence. How to use a comma seems to a mixed grab-bag of possibilities, but, in truth, there are rules to their usage.
Use commas to separate words and word groups in simple series of three or more items.
Example: Steve came to class with a compass, protractor, and ruler.
The above is using what is more commonly known as the Oxford comma. That would be the comma following the word 'protractor' since it precedes the 'and' in the sentence. It could be omitted and the sentence's meaning wouldn't be lost. Yet, in the following sentence, it would be helpful to help define the groupings.
Example: Steve ate meatloaf, macaroni and cheese and green beans.
Notice that 'macaroni and cheese' could also be construed as 'cheese and green beans' due to no comma, or even wosrse, a double 'and' with the listing of four items. By using the Oxford comma, the meaning becomes clearer.
Example: Steve ate meatloaf, macaron and cheese, and green beans.
Authors must decide if they will use the Oxford comma or not and be firm in their stand, not using it this time and then using it the next time. If the writer decides to eliminate the Oxford comma rule, s/he will only need to use it when confusion can be clarified, such as the macaroni and cheese example.
Use a comma to separate two adjectives when the adjectives are interchangeable.
Example: Elaine is a beautiful, young woman. OR Elaine is a young, beautiful woman.
A case where adjectives aren't interchangeable:
Example: He rented an expensive summer cottage. NOT He rented a summer expensive cottage.
Commas can be used to join two independent clauses using connectors such as and, or, but, nor, yet, etc.
This is done by placing the comma at the end of the first clause.
Example: He painted the house, and he mowed the lawn.
Notice there is a subject — he — in each clause and thereby demands a comma before the conjunction and. If the sentence was re-written, the comma could be deleted.
Example: He painted the house and mowed the lawn.
Notice how, by removing the subject of the second clause, it also removes the comma, thus including (and eliminating) the second clause to make it part of the first clause and using its subject.
Use a comma after words that introduce a sentence or set off expressions that break up the sentence flow.
No, I didn't mean that. OR I am, by the way, correct.
Words that start a sentence that might use a comma are well, yes, no, why, hello, hi, hey, generally, moreover, however and the list continues.
Rules could continue but here's a nice generalization that most writers know and basically need to just note.
- Separating a city from the state. Ex: I live in Bryan, Ohio.
- Names, nicknames and terms of endearment can be set off with commas. Ex: Yes, Thomas, I said that. OR Hey, honey, can you help me?
- Separating the date AND after the year. Ex: It was December 7, 1941, when Japan attacked Hawaii.
- Use commas to enclose degrees and 'full' names when mid-sentence. Ex: John Smith, PhD, spoke. OR My son, John Doe, Jr., is a doctor.
There are several other situations that entail rules but this should cover the most common usages. When in doubt, look it up. One items most reviewers despise is poor punctuation and lack of clarity in writing. Trust me, readers catch your errors faster than you believe since it jolts their reading.
Thanks for this clear explanation. Personally, I prefer to avoid the Oxford comma, except where its absence causes more confusion. We follow grammatical rules so that the reader understands what the writer intended.
I, too, prefer to only use the Oxford comment for clarity.
Lisa M. Collins
Really? I'm editing a client right now who uses Oxford and, to me, it is so cluttered. Sorry, personal opinion, I guess. LOL.
Commas are a touchy subject. I imagine in the literary world, comma wars have erupted, and prisoners were taken.
Many, not all, have given their lives in the editing process...
I am TERRIBLE at grammar. Thanks for explaining this Bob! I knew there were "different commas" but didn't know the difference. I'm pretty sure I'm one of those people who have used different types in different places and didn't know any different :o
I didn't know the one about the interchangeable adjectives. Thanks for the informative post.
Good job, Bob, especially on the Oxford comma, of which I'm a fan.
B,l,e,c,h,.... commas confuse me to no end and different editors also follow different rules. Yeesh.
Great post Bob. You're speaking my language here! Love the proper use of grammar!