As long as we’re on the subject of interjections, let’s also examine the punctuation of parenthetical expressions. Any word or phrase that interrupts a sentence should usually be set off by commas. These parenthetical elements offer supplemental information or informational afterthoughts, and usually a slight pause is intended:
I haven’t seen my best friend in a long time; indeed, it’s been more than a year since I last saw her.
I am planning a road trip to San Francisco to visit her; I am, in fact, leaving tomorrow morning.
I am excited to see her again, to say the least.
I am also excited, if not more excited, to meet her daughter for the first time.
There are always exceptions, however. Adverbs that are essential to the meaning of the sentence should not be set off by commas:
Los Angeles to San Francisco is indeed a long drive.
I am therefore making the trip with another friend.
Do you have a question about the comma? Let me know, and I’ll include it in a future installment of Mots Justes’ ongoing series.
The Mots Justes Series on Commas
Chicago Manual of Style, The. 15th ed. Chicago: The University of Chicago Press, 2003.
Hacker, Diana, The Bedford Handbook for Writers, 3rd ed. Boston: St. Martin’s Press: 1991.