Introduction to Commas

The comma ( , ) is a punctuation mark. It has the same shape as an apostrophe or single closing quotation mark in many typefaces, but it differs from them in being placed on the baseline of the text. Some typefaces render it as a small line, slightly curved or straight, or with the appearance of a small filled-in number 9.

The comma is used in many contexts and languages, principally for separating things. According to the Oxford English Dictionary, the word comma comes directly from the Greek komma (κόμμα), which means something cut off or a short clause.

In English, the comma is used mainly:

1. When “and”, “but” and “or” connect items within a sentence:

I have a book, a pen, and a pencil.

2. When “and”, “but”, and “or” connect two complete sentences:

I saw a cat, and you saw a mouse.

3. A comma is used at the end of a quoted sentence:

“Cats are fun to watch”, Jane said.

4. A comma is used at the end of a time clause when the time clause comes first in a sentence (clause is a structure that has a subject and a verb. These words introduce time clauses: “after”, “before”, “until”, “as soon as”,”while”, “when” :

Before I went to class, I ate breakfast.