Writing Tips

Series Commas

Many writers are not aware that full punctuation for a simple series (three or more elements) includes commas after every element in the series, including the last. That is:

... first, second, and last, ...

The comma preceding the conjunction is considered dispensable by many authorities. NIVA house style always retains the second comma, because we believe that its value as a signal to the reader outweighs the tiny typesetting gain from its omission.

On the other hand, the final comma is dispensable in most cases, being retained only where its use injects additional clarity into a text. The final comma is also the only comma typically used in a simple series of two.

Some Examples of Good Series Punctuation
Use no commas in a simple series of two:

• We ate apples and pears.
• We ate apples and drank iced tea.

Use full commas in a simple series of three or more:

• We ate apples, pears, and grapes.

Apply the same rules to embedded series:

• We ate apples, Bosc pears and Bartlett pears, and grapes.

When the sentence continues beyond the end of the series, the reader will appreciate the visual clue provided by a final comma:

• We ate apples and pears, and tossed the cores to the squirrels.

But, the usefulness of a final comma may be overridden by more pressing grammatical demands (in this case, a restrictive clause):

• We watched the ducks paddling on the lake and ate apples, pears, and grapes that we had bought at the local market.

A two-element series consisting of two lengthy independent clauses sometimes requires a separating comma:

• We ate apples, pears, and grapes that we had bought at the local market, and we drank iced tea that Ann had prepared that morning.

Shorter two-element series do not need punctuation:

• We ate and we drank our fill.

The conjunctions but, while, and yet represent a break in thought that may require a preceding comma even in a simple series of two:

• We sat in the shade, but got sunburned anyway.