Period After a Letter Used to Represent Someone's Real Last Name
Abbreviations
Rulebase Summary
If a letter is used to represent someone's last name and the letter chosen is the actual first letter of the name, use a period after the letter (Mrs. M., Patient R.). If the letter does not represent the real name — for example, when used as a placeholder like Mr. X or Motorist A — do not use the period after the letter.
Examples
Q. We won't say her last name, but did Mrs. M give you a phone number to call that night?
Q. We won't say her last name, but did Mrs. M. give you a phone number to call that night?
Letter represents the real first letter of the name — use a period.
Q. Did you meet Mr. X. in the station on April 10?
Q. Did you meet Mr. X in the station on April 10?
Letter is a generic placeholder, not a real name — no period.
Transcript Notes
The presence or absence of the period signals to the reader whether the letter is shorthand for a real name (period — name was withheld) or a generic placeholder (no period — invented for the example or to distinguish anonymous parties).
Style Guide References (1)
Morson's