Many kinds of abbreviations should be reserved for informal writing. Guidelines for how and when to use many of the most common types of abbreviations are outlined below.
When using abbreviations, make sure that your readers will be familiar with them. If they won’t be, then write out the full name (with the abbreviation in parentheses) on the first use.
Examples: Do they meet International Organization for Standardization (ISO) requirements?
Today the United Nations Organization (UNO) is having a mandatory meeting at 3 p.m.
Acronyms, abbreviations that spell a pronounceable word, never take periods.
Examples: How many countries are a part of NATO?
Today the NASDAQ closed 30 points higher than yesterday.
Titles with Proper Names
Titles that come immediately before or after proper names generally take periods.
Examples: If you see her, please tell Ms. Barker that I called.
Have you heard from Dr. Hansen today?
May I introduce you to our speaker, Mr. James Sanders Jr
Today I have an appointment with Deborah Bradshaw, D.D.S.
Our guest lecturer today is Rhonda Dalton, Ph.D.
Note: Some style guides prefer to omit the periods in academic degrees (such as D.D.S., M.D., and Ph.D.).
Do not abbreviate such titles when they do not accompany a proper name.
Not: Did you go to see the Dr. yesterday?
Can I help you, Mr.?
But: Did you go to see the doctor yesterday?
Can I help you, mister?
However, the abbreviations for academic degrees can be used alone when not used as part of a title
Examples: My brother will receive his Ph.D. in May.
Will you complete your B.A. this year?
Do not repeat titles or abbreviations at the end of a name if one or the other appeared at the beginning of the name.
Not: I’ll be taking the course from Professor William Fisher, Ph.D. But: The operation will be completed by Dr. Jonathan Tucker. Or: The operation will be completed by Jonathan Tucker, M.D. Or: I'll be taking the course from Professor William Fisher. Or: I'll be taking the course from William Fisher, Ph.D.
Titles of Corporations and Organizations
For names of organizations, corporations, colleges and universities, and agencies, periods are usually not used. Check the dictionary if you are not sure whether periods are needed.
Examples: He worked for AT&T for 30 years.
Jane will begin attending USC this fall.
Which is your favorite team in the NBA?
The NAACP has been around for years.
Dates and Times
Date designations are often accompanied by the abbreviations B.C., B.C.E., A.D., and C.E.
Examples: Wasn’t their civilization destroyed by about 400 B.C.?
I believe Constantinople lived around 300 A.D.
Expressions of time are likewise frequently accompanied by the abbreviations a.m. and p.m.
Examples: The plane will arrive at approximately 7 p.m.
He doesn’t like to be disturbed before 8:30 a.m.
Such abbreviations should not be used without specific date or time designations.
Not: We have a meeting this p.m. to discuss our new marketing strategy.
They will meet tomorrow a.m. to finalize the trip itinerary.
But: We have a meeting this afternoon to discuss our new marketing strategy.
They will meet tomorrow morning to finalize the trip itinerary.
Time zones, when abbreviated, should be capitalized. When not abbreviated, they are kept lowercase (with the exception of Pacific in Pacific standard or Pacific daylight time).
Examples: Did you say the broadcast would be at 8 a.m. EST?
The movie will start at 7 p.m. mountain daylight time.
The teleconference is scheduled for 10 a.m. Pacific standard time.
The terms daylight standard time and daylight saving time should not be capitalized and are not possessive.
Examples: Did you know that they changed the date that daylight saving time will end?
Latin abbreviations such as et al. (“and others”) and cf. (“compare”) are often used in footnotes and bibliographies. They are generally not used in running text.
Examples: Brown et al., The Players’ Guide, Fairfield, MA: Jameson Press, 2008.
For another interpretation of the work, cf. Thompson, Sometimes Knowing, 35.
Other Latin abbreviations, such as e.g. (for example), i.e. (that is) and etc. (et cetera) are also acceptable in informal writing, particularly when used in parenthetical expressions. However, such abbreviations should not be used in running text in formal writing.
Informal: The supplies that they needed (e.g., a tent, winter clothing, and food) were nearly impossible to come by.
The Spirit Committee (i.e., Amanda, Nicholas, Doug, and I) will begin planning the summer social tomorrow.
In the meeting they talked about all of the normal topics: overhead, revenue, human resources, resource management, etc.
Formal: The supplies that they needed (for instance, a tent, winter clothing, and food) were nearly impossible to come by.
The Spirit Committee (that is, Amanda, Nicholas, Doug, and I) will begin planning the summer social tomorrow.
In the meeting they talked about all of the normal topics: overhead, revenue, human resources, resource management, and so forth.
Do not use the U.S. Postal Service abbreviations of state names in regular text. Reserve these abbreviations for mailing addresses.
Not: Margaret Tanner, our director, lives in Galveston, TX
Next year, the convention will be held in Springfield, IL.
But: Margaret Tanner, our director, lives in Galveston, Texas
Next year, the convention will be held in Springfield, Illinois.
Also, do not use periods in these two-letter abbreviations.
Not: Please send your check to 111 Sunny Street Circle, Sunny City, F.L. 12345.
You can write him at 222 Bonnie Way, Fairfield, M.N. 99999.
But: Please send your check to 111 Sunny Street Circle, Sunny City, FL 12345.
You can write him at 222 Bonnie Way, Fairfield, MN 99999.
Terms of Measurement
For both the English and the metric system of measurement, the abbreviations are the same in singular and plural form.
When abbreviated, common terms of English measurement usually include the periods in general text (that is, in nonscientific text).
Examples: Their new home is 2500 sq. ft.
Yesterday she bought 5 lb. of sugar.
In scientific contexts, on the other hand, the periods are usually omitted.
Examples: 250 sq ft
But for most contexts, the English terms should be written out (see Inappropriate Abbreviations).
Examples: Their new home is 2500 square feet.
Yesterday she bought five pounds of sugar.
In the metric measurement system, periods are not used in abbreviations.
Examples: This solution contains 5 g of sodium.
The crater is at least 2 km deep.
Abbreviated Titles of Works
Abbreviations of titles of works that would be italicized should likewise be italicized.
Examples: Do you know what the OED says about it?
My favorite book is the CMS.
Possessive and Plural Forms
To write the possessive form for the abbreviation of a singular noun, add an apostrophe plus s.
Examples: That CPA’s salary is twice what mine is.
I’m not sure I understand the MDRA’s mission.
Do not use an apostrophe plus s to create the plural form of an abbreviation.
Not: There were three CNA’s at the meeting. Do you know how many students received their MBA’s last year?
Have you met any of the RN’s?
But: There were three CNAs at the meeting.
Do you know how many students received their MBAs last year?
Have you met any of the RNs?
To make the plural possessive form, add an apostrophe after the s only.
Examples: Have you heard the CPAs’ recommendations?
We understand the RNs’ desire to change their schedules.
Spacing in Abbreviations
When forming abbreviations, no space should come between the letters (or the letters and the periods) of the abbreviated form.
Examples: I believe John said she was a CEO.
How long have you worked as an FBI agent?
Initials in names, however, are separated by spaces.
Examples: Have you read this book by E. B. White?
Abbreviations with End Periods
When an abbreviation with periods comes at the end of a sentence, do not follow it with another period. One period is sufficient.
Not: The plane will arrive at approximately 7 p.m..
Yesterday I was introduced to John B. Warner Sr..
But: The plane will arrive at approximately 7 p.m.
Yesterday I was introduced to John B. Warner Sr.
A or An
Whether to use a or an in front of an abbreviation or acronym is determined by how the abbreviation is pronounced. If the abbreviation or acronym begins with a vowel sound, then an should be used; otherwise, a is used.
Examples: How long have you worked as an FBI agent?
The first stock I ever bought was in A T & T.
As indicated at the beginning of this article, some abbreviations are not appropriate in business or formal writing. For example, corporation designations should not be abbreviated unless the abbreviation is part of the official name of the company or firm.
Not: I once considered working for that co.
Yesterday I had the opportunity to meet Jensen & Larsen.
Did you have a chance to meet the Bart bros. yesterday?
But: I once considered working for that company. Or: I once considered working for Smith-Easton Co. Or: Yesterday I had the opportunity to meet (Mr.) Jensen and (Mr.) Larsen.
Yesterday I had the opportunity to meet the owners of Jensen & Larsen.
Or: Did you have a chance to meet the Bart brothers yesterday?
Have you ever heard of Bart Bros.?
In addition, geographical names; terms of measurement; names of days, months, and holidays; volume, chapter, section, and page designations; and names of school or college courses should be written out in general text. (Such terms would only be abbreviated in the most informal of contexts.)
Not: The Wilsons recently moved to Nev. from N. Dakota.
Did you say you wanted to buy 30 lbs.?
The meeting will be held on Thurs., Oct. 24.
In college, Lance majored in phys. ed.
Read pp. 23-37 of ch. 9 in the health manual to find out more information.
But: The Wilsons recently moved to Nevada from North Dakota.
Did you say you wanted to buy 30 pounds?
The meeting will be held on Thursday, October 24.
In college, Lance majored in physical education.
Read pages 23-37 of chapter 9 in the health manual to find out more information.