The comma is one of the most important punctuation marks in English, but it is often used wrongly. This page will introduce two of the most common uses of the comma: the conjoining use, and the listing use.
The listing useWhen you write a sentence containing a list of items, you will need to use a comma to separate the items. For example:
This sentence contains a list of four items. There are commas after coffee and sandwiches, to separate the items. After cheese, the word and is used instead; however, you can also include a comma BEFORE and if you like:
This comma is optional. However, you MUST include the word and.
The items in our example are all nouns, but almost anything can form a list in this way. Here are some more examples:
The conjoining useWhen you join two clauses together with a coordinating conjunction (such as and, but, so, and or), a comma is usually placed before the conjunction:
Here are examples using the most important coordinating conjunctions. You can get more information about coordinating conjunctions on the Basic Coordinating Conjunctions Web page.
Reversing the order of clausesWith conjunctions (such as because, as, since, while, and though) the dependent clause (the part beginning with the conjunction) can also come at the beginning of the sentence. In this case (and ONLY in this case), a comma can be used to join the two clauses together. Here are some examples: