names, suffixes, and credentials: comma use
Commas with a suffix such as Jr. or III, or a credential such as Ph.D., that follows a personal name.
No comma separates Jr., Sr., or a roman numeral from the name it follows, as in Martin Luther King Jr. and Henry Ford II.
A credential that follows a name is set off by commas: Samuel Ortiz, Ph.D., spoke first. A comma separates the credential from the name, and a second comma follows the credential whenever the sentence continues. The period that ends an abbreviation such as Ph.D. does not replace that second comma. When the credential ends the sentence, the period of the abbreviation also ends the sentence: The lecture was given by Samuel Ortiz, Ph.D.
A comma separates each of two or more credentials that follow a name: Grace Lin, M.D., Ph.D., directs the clinic. A name with both a suffix and a credential takes no comma before the suffix and a comma on each side of the credential: Paul Reyes Sr., D.D.S., retired last year.
See also titles before and after names; appositives: comma use; comma.
Examples
UseRobert Haines Jr. founded the firm in 1962. (No comma separates Jr. or Sr. from the name it follows.)
UseThe award went to Charles Avery III. (No comma separates a roman numeral from the name it follows.)
UseDana Okafor, Ph.D., leads the research team. (Commas set off a credential that follows a name.)
UseThe findings were reviewed by Elena Ruiz, M.D. (The period of an abbreviation that ends a sentence also ends the sentence.)
UseMorgan Ellis, Ph.D., R.N., will lead the study. (A comma separates each credential, and a comma follows the last one when the sentence continues.)
UseJames Porter Jr., M.D., joined the practice. (No comma separates Jr. from the name, and commas set off the credential that follows it.)
AvoidRobert Haines, Jr. founded the firm in 1962. (The comma before Jr. is incorrect, because no comma separates Jr. or Sr. from the name it follows. Write Robert Haines Jr. founded the firm in 1962, with no comma before Jr.)
AvoidDana Okafor, Ph.D. leads the research team. (A credential that follows a name takes a comma on each side when the sentence continues. Write Dana Okafor, Ph.D., leads the research team, with a comma after Ph.D.)