Commas to prevent confusion

In certain contexts, a comma is necessary to prevent confusion. If the writer has omitted a word or phrase, for example, a comma may be needed to signal the omission.

Example sentence with editing. Original sentence: To err is human; to forgive divine. Revised sentence: To err is human; to forgive, divine.

The comma replaces the verb is, which is clear from the first clause.

If two words in a row echo each other, a comma may be needed for ease of reading.

Example sentence with editing. Original sentence: All of the catastrophes that we had feared might happen happened. Revised sentence: All of the catastrophes that we had feared might happen, happened.

Sometimes a comma is needed to prevent readers from grouping words in ways that do not match the writer’s intention.

Example sentence with editing. Original sentence: Patients who can walk up and down the halls several times a day. Revised sentence: Patients who can, walk up and down the halls several times a day.

Exercise: Major uses of the comma 1

Exercise: Major uses of the comma 2

Exercise: All uses of the comma