Punctuation

Commas with appositives

An appositive is a noun or noun phrase that renames a nearby noun. Nonrestrictive appositives are set off with commas; restrictive appositives are not.

Heading: Nonrestrictive appositive (with commas). Example sentence with editing. Original sentence: Darwin's most important book On the Origin of Species was the results of many years of research. Revised sentence: Darwin's most important book, On the Origin of Species, was the results of many years of research.

Most important restricts the meaning to one book, so the appositive On the Origin of Species is nonrestrictive and should be set off with commas.

Heading: Nonrestrictive appositive (with comma). Example sentence with editing. Original sentence: The doctor prescribed albuterol a bronchial dilator. Revised sentence: The doctor prescribed albuterol, a bronchial dilator.

Albuterol is a specific drug; a bronchial dilator adds useful but not essential information, so it is set off with commas.

Heading: Restrictive appositive (no commas). Example sentence with editing. Original sentence: The song, “Vertigo,” was blasted out of huge amplifiers. Revised sentence: The song “Vertigo” was blasted out of huge amplifiers.

Once they’ve read song, readers still don’t know precisely which song the writer means. The appositive following song restricts its meaning.

Heading: Restrictive appositive (no commas). Example sentence with editing. Original sentence: The English word, piano, comes from the Italian word for “soft” or “quiet.” Revised sentence: The English word piano comes from the Italian word for “soft” or “quiet.”

The sentence does not make sense without specifying the exact English word, so it cannot be set off with commas.

Exercises:

Major uses of the comma 1

Major uses of the comma 2

All uses of the comma