Punctuation

No comma between some compound elements

Though it is correct to use a comma before a coordinating conjunction joining independent clauses, this rule should not be extended to other compound word groups.

Example sentence with editing. Original sentence: Marie Curie discovered radium, and later applied her work on radioactivity to medicine. Revised sentence: Marie Curie discovered radium and later applied her work on radioactivity to medicine.

And links two verbs in a compound predicate: discovered and applied.

Example sentence with editing. Original sentence: Jake still does not realize that his illness is serious, and that he will have to alert his diet to improve. Revised sentence: Jake still does not realize that his illness is serious and that he will have to alert his diet to improve.

And links two subordinate clauses, each beginning with that.

EXCEPTION:If three elements form a compound, commas should be used to separate all the elements.

Example sentence with editing. Original sentence: The head of the Federal Reserve Board was expected to comment on rising inflation to keep the prime interest rate at 5.25% and to recommend increasing oil reserves. Revised sentence: The head of the Federal Reserve Board was expected to comment on rising inflation, to keep the prime interest rate at 5.25%, and to recommend increasing oil reserves.

The phrases beginning with to form a compound direct object and should be separated with commas.

Exercises:

Misuses of the comma 1

Misuses of the comma 2