Abbreviations work like road signs with picture symbols instead of words. Instead of writing out "do not enter," you see a symbol of a red circle with a red line through it. Instead of writing out " road crews working," you see a sign with a symbol representing a person at work. The signs--like abbreviations--condense words and come to represent those words.

Often, it is an open question whether or not to use periods with abbreviations. According to the Chicago Manual of Style the trend is strongly away from using periods with all kinds of abbreviations that have carried them in the past.

Abbreviations of certain words, titles, and phrases are common in English. In general, write out words completely in sentences except in the following situations:

• commonly-known titles of organizations (NATO, YMCA, CIA, NOW)
• titles of persons, either before or after the name (Mr., Ms., Dr., Ph.D., Jr., Rev.)
• U.S. Postal Service abbreviations.

Note: Give credit for degrees either before or after a person's name, not both:

Incorrect: Dr. Dennis Smith, Ph.D
Correct: Dr. Dennis Smith or Dennis Smith, Ph.D.

• "time-related" abbreviations (a.m., p.m., B.C., A.D., B.C.E., C.E.)

Note: a.m. and p.m. are usually not capitalized or are small capitals.

standard abbreviations in writing, which are often abbreviations of Latin phrases such as:

i.e. (id est) - that is
cf. (confer) - compare
e.g. (exempli gratia) - for example
et al. (et alii) - and others
etc. (et cetera)- and other things
N.B. (nota bene) - note well

Note: Such abbreviations are usually used in tables, source citations, and comments inside parentheses in formal writing. Avoid their use in academic or formal writing.

• technical jargon, trade names (mph, DOS, IBM)

Note: Inc., Bros., Co., or & should only be used in official names of businesses.

Incorrect: The Howard bros. own construction companies in both New York & Santa Fe.
Correct: The Howard brothers own construction companies in both New York and Santa Fe.
Correct: Howard Bros. is a construction company that operates in New York and Santa Fe.

Spell out units of measurement, names of places, courses, time, calendar designations and divisions in books when writing sentences. These abbreviations are appropriate on forms, reports and statistic sheets.

Incorrect: The wall is forty in. high and a ft deep.
Correct: The wall is forty inches high and a foot deep.

Incorrect: We live in NY but spend Aug. and Sept. in ME.
Correct: We live in New York but spend August and September in Maine.

Incorrect: I love my bio course, but I'm struggling in poli sci.
Correct: I love my biology course, but I'm struggling in political science.

Incorrect: Paul quit his job on Fri., Nov. 13, which we superstitious types thought did not bode well.
Correct: Paul quit his job on Friday, November 13, which we superstitious types thought did not bode well.

Incorrect: Jeanie read pp. 35-69 the first night and then ch. 8 in the same bk. the next night.
Correct: Jeanie read pages 35-69 the first night and then chapter 8 in the same book the next night.

Capitalize abbreviations if the whole word would be capitalized when written out.

The CEO of Ford retired today.
Tips: The ampersand (&) is an abbreviation for and, but it should only be used in a title or name:
Peter, Paul & Mary; Car & Driver magazine

Symbols are appropriate in technical and scientific writing (%, >,+,=), but in other academic papers the symbols should be spelled out:

Incorrect: Hannah was told that 65% of all adults in the U.S. do not eat five servings of fruits and vegetables a day.
Correct: Hannah was told that 65 percent of all adults in the U.S. do not eat five servings of fruits and vegetables a day.

The money sign ($) should only be used if numbers follow it. Also, don't use both the money sign and the word.

Incorrect: He found 50 cents.
Correct: He found $40.