Abbreviations (Part One)

In this week’s lesson, we’re going to begin examining abbreviations. English punctuation and capitalization rules for abbreviations vary widely because those rules frequently change. Moreover, American and British English differ in the use of periods with names and titles of people.

As a general rule, you should avoid abbreviations in formal writing unless you are sure that the abbreviations you are using will be familiar to your audience. The situation is somewhat different in scientific and technical writing. Depending on your specific field, it may be acceptable or even preferable to use agreed upon abbreviations for complex terms. If you are unsure what is and is not an acceptable abbreviation at your company, we recommend consulting your company’s style guide. With those caveats in mind, here are some generally-agreed upon guidelines for writing abbreviations in modern American English.

The current trend is to write abbreviation without periods. However, it is acceptable to write many abbreviations with or without periods:

PhD or Ph.D.             BA or B.A.

USA or U.S.A.            PM or P.M. OR p.m.

Abbreviations composed of all capital letters do not usually have periods or spaces between letters:

GA (Georgia)

PIN (Personal Identification Number)

TEI (The English Island)*


UN (United Nations)

*Where “the” comes at the beginning and is part of the official name.

Abbreviations composed of or ending in lowercase letters usually have a period at the end and no periods or spaces between letters:

Ave. (Avenue)

Inc. (Incorporated)

Mr. (Mister)

One notable exception to the above rule is abbreviations for units of measure:

cm (centimeters)

km (kilometers)

mph (miles per hour)


Titles of People         


You should always abbreviate titles that appear before or after people’s names. Certain titles always go before a person’s name:

Mr. Green

Mrs. White

Ms. Marvel

Miss Jones

Prof. Plum

Rev. King

Note: “Miss” in not an abbreviation and should not be followed by a period. In professional settings, Ms. is generally preferred over Miss/Mrs. when address a woman who has not earned a doctoral degree.

Other titles go after a person’s name:

Megan Roberts, RN (R.N.)

Kennedy Johnson, MA (M.A.)

Allison Henderson, CPA (C.P.A)

Phillip J. Smith, Esq.


Medical doctors and other medical professionals can have a title either before or after their names:

Dr. Jamie Hong          OR      Jamie Hong, DDS (D.D.S.)

Dr. Hector Rodriguez OR      Hector Rodriguez, MD (M.D.)

Dr. Sandra Kelley       OR      Sandra Kelley, PhD (Ph.D.)