A common mistake students make is thinking that a comma is merely a "breath mark;" an indication of a pause you might make if you were speaking the text. In a way this is true—but not completely.
First, you have to follow the rules for using commas. Then you may have some freedom to use commas to create "natural-sounding" pauses in the text.
The following rules are taken from three sources:
1 - My favorite color is red.
2 - My favorite colors are red and yellow.
3 - My favorite colors are red, yellow, and green.
4 - My favorite colors are red, yellow, green, and mauve.
Especially note that last comma, before the conjunction and, where there are three or more items in the list. That's the one many students miss.
My brother, needless to say, wanted to borrow money.
Note that besides being good grammar, this is also good vocal cadencing. And that's just a fancy way of saying that it sounds natural to put short pauses at the commas when speaking this line. Try it yourself and see.
There are times when the commas aren't necessary:
It was apparent beyond anyone's doubt that he had made a terrible mistake.
You can see that the text in red might have been put between a pair of commas, though it works just fine without them.
At any rate, never use one comma and not the other in this kind of parenthetical situation. This sentence either needs both commas, or neither.
Some of these inner clauses can be restrictive:
The seashells that are prettier than the others tend to get picked up by beachcombers.
We're not talking about all seashells. In this statement, we're restricting (limiting) ourselves only to the ones that are prettier. That makes the red clause restrictive. On the other hand...
New batches of seashells, thrown onto the beach daily by the tide, were picked up by beachcombers.
Note that the blue phrase is not restrictive. It does not reduce the number of seashells to a smaller grouping. It is additive. It adds information about the Subject, without making it smaller. It's telling us where the shells came from.
The key here is that:
Here are some more examples of these kinds of clauses. Think about them carefully and see how they are, in fact, restrictive or additive:
The numbers can be:
There are two rules for putting commas in dates:
Here are some examples:
February to July, 1972
April 6, 1936
Wednesday, November 13, 1929
There's another, unpunctuated, form you can sometimes find in academic writing:
6 April 1943
This is also a fine form for a date. Just be aware you should reserve it for documentary or academic writing.
There are many different subordinating conjunctions, which glue these clauses together in all kinds of interesting ways. They can be individual words or idiomatic phrases. Here are a few:
But by now you should be asking yourself, "All this is wonderful, but what is the comma rule?" "Cut to the chase!!!"
There is an alternate way to express these kinds of ideas. You can begin the sentence with the subordinating conjunction:
But notice that you need something between the two clauses! If the conjunction isn't there, you'll need a comma.
DISCLAIMER: This illustration of correct comma usage is not intended to imply that Ron A. Zajac, his Administration, Faculty, or Staff directly or indirectly endorse gambling in general or state lotteries specifically.