These last comma reminders wrap up 99.44% of all the commas writers need. Who can’t learn a set of rules reduced to the number of fingers on one hand?

Comma Rule Number 4

Interjections and forms of address are set off with commas.

Yes, I will accompany you to the ball.                            No, I won’t!

You, sir, are out of line.       You may be assured, ma’am, of our concern.

Are you certain of that prognosis, Doctor?

Thank you, Mother, for all you do.

There’s a world of difference between “Let’s eat, Grandpa” and “Let’s eat Grandpa.”

 

Comma Rule Number 5

Words, phrases, or clauses (appositives and infinitives included) which interrupt the main clause must be set off with commas fore and aft. The rule includes the state following the name of a city and the year following the day of the month.

Mrs. Ellen Bennet, my mother, is in the drawing room.

The Brooklyn Bridge, as opposed to this matchstick construction, is sturdy and reliable.

He was born on June 23, 1941, near Big Timber, Montana, along the Yellowstone River.

Those earrings, in my opinion, would look better hanging over formal dining tables.

5A. The final necessary use of the comma is the most difficult for many writers. It’s actually the same as rule 5, but it’s often presented in isolation because of its difficulty. As with appositives and infinitive phrases, it separates nonrestrictive clauses in a sentence. The nonrestrictive clause is not essential to the sentence. It merely adds information:

Abraham Lincoln, who was the tallest of U.S. presidents, was an imposing figure of a man.

The grizzly, a bear misunderstood by tourists, is named Ursus horribilis for good reason. 

By contrast, a restrictive clause is essential to the sentence:

The lady who cried is my mother.

The man who shot Liberty Valance became a state senator.