Grammar Tip – Periods With Abbreviations

Mary Lou’s question: “Why is it that MD does not have a period after the M. and D. as this is a title?”

BizWritingTip response: The rule for abbreviations is that if they are composed of all capital letters, you do not use periods with them.

Examples
MD
YMCA
MP
SOPs (standard operating procedures)

Exception: Abbreviations that are geographical, refer to a person, or are a single letter, do have periods.

Examples
U.S.A.
P.E.I.
John A. Macdonald
S. (but SW is correct — two letters)

Most abbreviations made up of lowercase letters or that are a mixture of upper and lowercase do contain periods.

Examples
P.Eng.
B.Sc.
Inc.
i.e. or e.g.
Mr. or Mrs.

However, according to The Canadian Press Caps and Spelling mixed abbreviations that start and end with a capital letter do not contain periods.

Examples
U of T
PhD

Aren’t you glad you asked?