Punctuation

No comma with an essential concluding adverb clause

It is typical to set off introductory adverb clauses with a comma. When adverb clauses conclude a sentence, however, they are not set off by commas if they restrict the meaning of the earlier part of the sentence.

Essential adverb clauses

Adverb clauses beginning with after, as soon as, before, because, if, since, unless, until, and when are usually essential.

Example sentence with editing. Original sentence: Don't visit Paris at the height of the tourist season, unless you have booked hotel reservations. Revised sentence: Don't visit Paris at the height of the tourist season unless you have booked hotel reservations.

Example sentence with editing. Original sentence: Villagers had no early warning signal, because the power to the siren had been disconnected. Revised sentence: Villagers had no early warning signal because the power to the siren had been disconnected.

Example sentence with editing. Original sentence: Each rule violation must be reported to the official on the course, before a subsequent shot is taken. Revised sentence: Each rule violation must be reported to the official on the course before a subsequent shot is taken.

In each case, the adverb clause provides essential information that changes the meaning (restricts) the informtion in the independent clause.

Nonessential adverb clauses

When a concluding adverb clause is nonessential, it should be preceded by a comma. Clauses beginning with although, even though, though, and whereas are usually nonessential.

Example sentence with editing. Original sentence: The lecture seemed to last only a short time although the clock said it had gone on for more than an hour. Revised sentence: The lecture seemed to last only a short time, although the clock said it had gone on for more than an hour.

Example sentence with editing. Original sentence: The water was judged to be drinkable even though it contained minute specks of particulate matter. Revised sentence: The water was judged to be drinkable, even though it contained minute specks of particulate matter.

Example sentence with editing. Original sentence: The owner of the plumbing supply house was found guilty of fraud whereas his business partner had all charges against him dismissed. Revised sentence: The owner of the plumbing supply house was found guilty of fraud, whereas his business partner had all charges against him dismissed.

Exercises:

Misuses of the comma 1

Misuses of the comma 2