Abbreviations are shortened forms of words; acronyms are abbreviations formed by using the first letter of each word to form a pronounceable word. Contractions are also abbreviations formed by using an apostrophe to show omitted letters or numbers. (Contractions are used only in informal writing.) Use an abbreviation only if its meaning is clear.

Follow these rules when using abbreviations:

  1. First Time Abbreviating
    • The California State University, Chico (CSUC) graduation ceremony will be held this Saturday. CSUC will graduate 2,700 students this year.
  2. Abbreviate Commonly–Known Terms
    • PC
    • TV
    • ATM
  3. Abbreviate Courtesy Titles and Personal Titles
    Abbreviate courtesy titles and personal titles. Abbreviate academic and professional titles only when they follow a name or when they are used with the full name or initials and the last name. Use a comma before and after an abbreviation in a sentence, except with the abbreviations Jr. and Sr.
    • Mr. Ms. Dr. Laura Thomas, MD Professor Soliz Prof. Jorge Soliz Prof. J.R. Soliz
    • Nancy Wright, RN, was promoted to head nurse.
    • Roger Palmer Sr. led the project.
  4. Well-Known Businesses
    Abbreviations are acceptable for well–known businesses and organizations.
    • FBI
    • CBS
    • MGM
  5. Time Markers
    Use the abbreviations BC and AD, without periods, to indicate dates. BC always follows the year, but AD may follow or precede the year.
    • 400 BC
    • 400 AD
    • AD 400
  6. Dates
    Abbreviate months and days of the week only when they are part of a full date or in a chart where space is limited.
    • Dec. 16, 1963
    • Mon. Dec. 16, 1963
  7. Clock Time
    Use abbreviations for clock time. Use capital letters and periods, capital letters and no periods, or lowercase letters and periods. Just be consistent. DO NOT abbreviate clock time when no number is attached to the abbreviation.
    • 7:30 A.M.
    • 7:30 AM
    • 7:30 a.m.
    • CORRECT: The meeting is in the morning.
    • INCORRECT: The meeting is in the a.m.
  8. Time Zones
    Use abbreviations, without periods, for time zones.
    • EST
    • MST
    • PDT
  9. Measurements
    Measurements should be spelled out, not abbreviated, except in tables and charts.
    • CORRECT: inches
    • INCORRECT: in.
    • CORRECT: miles per hour
    • INCORRECT: mph
  10. The Word "Number"
    The word number may be abbreviated when it is followed by a figure; otherwise, spell it out.
    • No. 65
    • The number I want is 65.
  11. State Names on Letters
    Use abbreviations for U.S. state names on envelopes and in the inside address of a letter. Generally, spell out the full state name in text. Street addresses can either be abbreviated or spelled out in text. When indicating direction before a street name, spell out North, South, East, and West. However, compound directions (N.W. or S.W.) after a street name may be abbreviated.
    • The meeting will be held at 1212 R Street, Sacramento, California.
    • Meet me at 1234 North Maple St., San Diego, CA

Punctuation and Capitalization

Abbreviations also have specific rules for punctuation and capitalization. See below for the specific rules on how to punctuate and capitalize certain abbreviations:

Use periods in most abbreviations that contain lowercase letters. Do not use periods in most professional titles, the names of well–known businesses and organizations, and acronyms.

  • f.o.b.
  • e.g.
  • p.m.
  • CPA
  • CLU
  • CFP
  • CBS
  • IBM
  • NRA
  • radar (radio detecting and ranging)
  • snafu (situation normal: all fouled up) 

When an abbreviation comes at the end of a sentence, use only one period. However, place question marks or exclamation marks after the period in the abbreviation.

  • I awoke at 7:15 a.m.
  • Did you go to work at 8:00 a.m.? 

Generally, rules for capitalizing abbreviations follow the rules for capitalizing the original words. Proper nouns are capitalized in abbreviations; common nouns are not.

  • NAACP 
  • c.o.d. 
  • FAA 

Use an apostrophe to show when letters of a word have been omitted in a contraction. DO NOT use the
apostrophe when the abbreviation already shows omission of letters.

  • aren't cont. (NOT cont 'd) 
  • Attn. (NOT Att'n)