Abbreviate the following:

• Titles before names: Mrs., Mr., Ms., Prof., Dr., Gen., Rep., Sen., St. (for Saint)
  Notice that Miss is not an abbreviation, so we don't put a period after it. Ms. is not an abbreviation, either, but we do use a period after it. Go figure.

  The plural of Mr. is Messrs. (We invited Messrs. Carter, Lincoln, and Ford.) The plural of Dr. is Drs. (We consulted Drs. Carter, Lincoln, and Ford.) The plural of Mrs. is Mrs.

  In most formal prose, we do not use titles, abbreviated or otherwise, with individuals. Ms. Emily Dickinson is simply Emily Dickinson, and after the first use of her full name, Dickinson will do (unless we need Emily to avoid confusion with other Dickinsons).

  The abbreviation Rev. (for Reverend) is not, strictly speaking, a title; it is an adjective. It should, then, be used in this way: "We invited the Rev. Alan Darling" or "We invited the Rev. Mr. Darling," but not "We invited the Rev. Darling." We cannot say "We invited the reverend to dinner" and only a cad would invite the rev.

• Titles after names: Sr., Jr., Ph.D., M.D., B.A., M.A., D.D.S.
  These are standard abbreviations, with periods. The APA Publication Manual recommends not using periods with degrees. All sources advise against using titles before and after a name at the same time (i.e., she can be Dr. Juanita Espinoza or Juanita Espinoza, Ph.D., but she can't be Dr. Juanita Espinoza, Ph.D). And we do not abbreviate a title that isn't attached to a name: "We went to see the doctor (not dr.) yesterday."
• Names of
  • familiar institutions -- UConn, MIT, UCLA, CIA, FBI, NATO
  • countries -- U.S.A., U.K.
  • corporations -- IBM, CBS, NPR, CNN, ITT
  • famous people -- LBJ, FDR, JFK
  • very familiar objects -- TV, VCR, CD-ROM.
  Notice that U.S.A. can also be written USA, but U.S. is better with the periods. Also, we can use U.S. as a modifier (the U.S. policy on immigration) but not as a noun (He left the U.S.).
• Terms of mathematical units: 15 in., 15 ft, 15 kg, 15 m, 15 lb

  Generally, you would use these abbreviations only in technical writing. Notice that we do not put an s after such abbreviations even when the plural is indicated. Also, we do not use a period with such abbreviations except for in., which could be confused with the preposition in.

• Long, common phrases, such as IQ (Intelligence Quotient), rpm (revolutions per minute), mph (miles per hour), and mpg (miles per gallon).
  Such abbreviations are acceptable even in formal academic text and may be used without periods.
• Words used with numbers: He left at 2:00 a.m. She was born in 1520 B.C.

  Either lower or upper case letters can be used with A.M., a.m., P.M., p.m. The abbreviation B.C. (before Christ) is used after the date; A.D. (anno domini, "in the year of the Lord") appears before the date. The abbreviations B.C. and A.D. are sometimes replaced with B.C.E. (before the common era) and C.E. (common era), both used after the date (although one must add that those abbreviations are neither widely used nor commonly understood).

  It is considered bad form to use these abbreviations without a specific number attached to them: "We'll do this in the a.m." or "We'll do this tomorrow a.m."

• Common Latin terms: etc. (et cetera -- and so forth), i.e. (id est -- that is), e.g. (exempli gratia -- for example), et al. (et alii -- and others).

  The abbreviation i.e. (i.e., that is) is often confused with other abbreviations (e.g., e.g.). Do not italicize or underline these abbreviations. Most sources say to avoid using Latin abbreviations except within parenthetical notes and some sources say not to use Latin abbreviations at all (use the English terms instead) except within citations or reference lists. Good advice.

• Names of states and territories in references and addresses, but not in normal text. Abbreviations accepted by the U.S. Postal Service are listed online. Do not use state abbreviations simply to save time or space except in an address on an envelope or list. We do not use periods with state abbreviations: CT, NY, NJ. We use D.C. after the name of the city within the District of Columbia: Washington, D.C.; the APA Manual does not use periods with DC.

Don't abbreviate the following:
(In formal academic prose it is considered bad form to abbreviate words simply to save space, time, or energy.)

• Words such as through (thru), night (nite).
• Days of the week or months of the year.
• Words at the beginning of a sentence.
• People's names such as Chas. (for Charles) or Jas. (for James), unless those abbreviations have come to be accepted as nicknames.
• Courses such as econ (for economics) or poli sci (for political science).