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ABBREVIATIONS

See also LETTERS OF THE ALPHABET, PLURALS.

In general, abbreviations should be avoided in text and legends, at least on first use, except for a few standard forms (a.m., B.C., etc.). Many common abbreviations are listed in this stylebook. If an entry is not here, follow the first form listed in the latest edition of Webster's.

1. Plurals of abbreviations without periods are generally formed with s, no apostrophe:
 
 
GIs
TVs
MPs
VIPs
VCRs
UFOs
PCBs
IOUs
S&Ls
C-54s
type 2s
CD-ROMs

  If a double s combination occurs, add apostrophe plus s:
    SOS's

Plurals of abbreviations with periods and of letters of the alphabet used as nouns take apostrophe plus s. Plurals of italicized letters add italic apostrophe plus roman s:
    Ph.D.'s
ABC's

Model A's
Model T's
p's and q's
his Scottish r's
straight A's
 
  Plurals of noun abbreviations with a single period usually add only s:
    vol., vols.
       
  Plurals of Btu and rpm and of abbreviations for metric units are the same as the singular:
    12,000 Btu
2,000 rpm
2 m
23 mg
11.64 L.
100 cm
 
2. Days and months are not abbreviated in text or legends but may be abbreviated in footnotes and map notes. See also DAYS , WEEK, MONTHS.
3. Units of time are not abbreviated in text or legends but may be abbreviated in footnotes and map notes and used without periods for design reasons. The following abbreviations are both singular and plural:
    sec.
min.
hr.
wk.
mo.
yr.
day(s), (do not abbreviate)  
4. The books of the Bible are not abbreviated and are set in roman without quotation marks.
5. Geographic names are spelled out in both text and legends, with very few exceptions such as D.C., U.S., and C.I.S. Spell out United States on first appearance. Generally abbreviate Saint but not Fort or Mount. On maps, abbreviations such as St. and Ave. may be used.
6. Ordinal numerals are spelled out through tenth, above that: 11th, 21st, 32nd, 43rd.
7. Map coordinates and compass directions: latitude 72° 54' N, longitude 165° 53' W (note spaces and comma); 21° north (first use); 21° N; NE, SW, WNW.
8. Weights and measures may be abbreviated in credit lines and map notes. Such abbreviations do not take periods; plurals do not add s or es:
    vase 12 cm
8-in snake
16 mm
f/22
11 sq mi
three hr
11 min 30 sec
49-yr span
 
  See also METRIC AND INTERNATIONAL MEASUREMENT.
9. Organizations and individuals: If there is much material about an organization, give its full name at least once; however, well-known names may be shortened even on first appearance and do not take periods: DuPont, IBM, Ford, MIT, Caltech, UCLA, UN, UNESCO, USGS. Generally do not abbreviate Company or Corporation or use an ampersand unless it is so done on the organization's letterhead. Limited Liability Company may be abbreviated as LLC (no periods). With individuals, no periods are needed: FDR, JFK, LBJ, but T. R.
10. Civilian titles: The following titles are always abbreviated with a proper name: Mr., Mrs., Ms., Dr., Sr., and Jr. (with commas before and after Sr. and Jr. with full name). Certain titles are normally not abbreviated:
    President
Secretary
Congressman
the Reverend
Vice President
Senator
Ambassador
Professor
Governor
Representative
Mayor
the Honorable
 
11. Military titles on first appearance are abbreviated with full name: Lt. Gen. David Wooddell. Subsequently, use last name only with appropriate part of title spelled out: General Poole. When a military rank is used with a title of nobility or royalty, spell out the military rank: Admiral Lord Mountbatten.

See MILITARY RANKS for a listing of ranks with abbreviations and use.