Commas separate three or more items in a series. It is optional to use a comma before the last item, but it is generally safer to use it. Frank played baseball, hockey, and football in high school. A comma separates two or more adjectives in a row if the adjectives can switch positions without changing the meaning. The sunny, cool day was perfect for lying in the dark green grass.
Commas separate two or more items in an address or date.
My new address is 4604 Linden Court, San Diego, California 92213. I hope you will call me on December 15. Dear Alice, Yours truly, A comma separates a tag question from the rest of a sentence. Ron wore cowboy boots, and Jeff wore tennis shoes. A comma separates a dependent clause from an independent clause when the dependent clause appears before the independent clause.