Often names—either of people or of things—are accompanied by suffixes or other extra information that may or may not need to be set off by commas.
It used to be that generational name suffixes like Jr. and Sr. were set off by commas. This is no longer necessary:
John Jr. is the son of John.
If commas are used, however, they should appear both before and after the suffix:
John, Jr., is the son of John.
Never use commas with generational suffixes III, IV, etc.:
If John Jr. has a son named John, he will be John III.
Likewise, commas are no longer necessary to set off elements such as Inc., Ltd., etc.:
Readers are eager to catch a glimpse of the new ereader from Apple Inc.
If commas are used, however, they should appear both before and after the element:
Readers are eager to catch a glimpse of the new ereader from Apple, Inc.
Do, however, use commas to set off a person’s title if it follows his or her name:
Mehmet Oz, MD, has segued from medicine to television.
Finally, personal names are sometimes followed by the person’s place of residence. Whether you should use commas to set off this information depends on whether it is necessary to understanding the meaning of the sentence. If it’s extra, parenthetical information, use commas; if it’s essential information, don’t:
Stephanie Herseth, of Houghton, is my home state of South Dakota’s only U.S. Congressperson.
The Herseths of South Dakota have been involved in politics since her grandfather’s generation.
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.