Using a comma with an adverbial clause

A comma is required before or after an adverbial clause, depending on whether it begins or ends a sentence, and if it functions as a nonrestrictive clause. A nonrestrictive clause is not essential for the reader to understand the full meaning of the word or words that it modifies. It simply adds more information, describing but not limiting (“restricting”) what it modifies. (For more info about restrictive and nonrestrictive clauses, see my earlier post “Which hunting.”)

Look at this example:

When Charley woke up a horrible stench filled the room.

I have underlined the adverbial clause. It’s nonrestrictive in this sentence, so you should place a comma after the word up. Then readers won’t misread the sentence and think that Charley woke up a horrible stench.

For the same reason you should put a comma after the adverbial clause in this cannibalistic sentence:

When we had finished eating Robert and I left the room.

Poor Robert!


Paul Thayer
My book editing website

Using commas to avoid misreading

Sometimes you need to insert a comma for no other reason than to avoid the misreading of a sentence.

Consider these two sentences:

In the place where the willow grew the river was broad and slow.

Once he had been allowed to attend the exorcism of a boy in rural Nigeria.

These sentences could be easily misread. In the first sentence the reader may think you’re saying that the willow tree grew the river (that would be something to see) unless you place a comma after the word grew.

In the second sentence, if you don’t put a comma after the first word, Once, the reader will take that word as a conjunction that means “at the moment when” or “as soon as.” If you use this word as an adverb, it means “at some indefinite time in the past.” To communicate that meaning you have to place a comma after Once.

More examples:

As we would expect Freud’s self-evaluation would hardly be agreed upon by everyone.

To clarify the meaning of this sentence, you should place a comma after the word expect.

When I woke up Annette was looking down at me.

The first-person narrator did not wake up Annette. He woke up and saw her looking down at him. To make that clear, put a comma after the word up.

When we had finished eating Robert and I left the room.

Unless you’re writing about cannibals (“Pass the salt, please”), nobody ate Robert. Lucky for him. Put a comma after the word eating.

Two cannibals are eating a clown. One of the cannibals asks the other one, "Does this taste funny to you?"

Paul Thayer

Your Book Editor