Abbreviations for Name Suffixes
To abbreviate name suffixes such as “junior” and “senior,” the first and last letters -- “j” and “r” for “junior” and “s” and “r” for senior -- are written followed by a period. This abbreviation is used when a person’s given name is written in full such as John H. Smith Jr. When used in this context, the abbreviation is capitalized and a period follows it. If the name is written last name first, it should follow this pattern: Last Name, First Name Middle Initial., Suffix. For example, “Williams, Mark A., III.”
Comma Usage with Name Suffixes
In the past, a comma separated the last name from the suffix; however, most style guides no longer separate the last name from the suffix with a comma. For example, a name is written “Richard A. Black Sr.,” not “Richard A. Black, Sr.” A comma is used after the period following the abbreviation if the sentence continues beyond the name as the example above illustrates. Note that if a person goes by the name “Junior,” and it is not being used as a suffix, the name should be written out and not abbreviated.