2. the signaling of a separate idea (example: The movie was, in my opinion, wonderful!)
3. a listing of similar items grouped together (example: red, orange, yellow and green)
4. separates the day of the month from the year (example: June 15, 2014)
5. separates a city from a state (example: Los Angeles, California)
6. the end of a greeting or closing in a letter (example: Dear John, and Truly yours,)
When listing only two items, no comma is needed. Example: John and Mark. However, when listing three or more items in a row, a comma is used to separate the listed items: Example: boats, trains, planes and cars are all modes of transportation. [NOTE: A comma appears before words of conjunctions such as and, but, or, nor, so and yet.] If that is the case, then why is there no comma in our above example between “planes and cars?” The general rule is that if you are listing a series of items a comma does not appear between the next to last and last item. The word “and” here replaces the need for a comma. However, when you are linking two sentences together (known as a compound sentence), the comma is used to show the end of one sentence and the beginning of the next sentence such as in the example: “She studied mathematics, and she also studied foreign languages.”]