Abbreviations have a long history, created so that spelling out a whole word could be avoided. This might be done to save time and space, and also to provide secrecy. Shortened words were used and initial letters were commonly used to represent words in specific applications. In classical Greece and Rome, the reduction of words to single letters was common. In Roman inscriptions, "Words were commonly abbreviated by using the initial letter or letters of words, and most inscriptions have at least one abbreviation." However, "some could have more than one meaning, depending on their context. (For example, A can be an abbreviation for many words, such as ager, amicus, annus, as, Aulus, Aurelius, aurum and avus.)"
Abbreviations in English were frequently used from its earliest days. Manuscripts of copies of the old English poem Beowulf used many abbreviations, for example 7 or & for and, and y for since, so that "not much space is wasted". The standardisation of English in the 15th through 17th centuries included such a growth in the use of abbreviations. At first, abbreviations were sometimes represented with various suspension signs, not only periods. For example, sequences like ‹er› were replaced with ‹ɔ›, as in ‹mastɔ› for master and ‹exacɔbate› for exacerbate. While this may seem trivial, it was symptomatic of an attempt by people manually reproducing academic texts to reduce the copy time. An example from the Oxford University Register, 1503:
Mastɔ subwardenɔ y ɔmēde me to you. And wherɔ y wrot to you the last wyke that y trouyde itt good to differrɔ thelectionɔ ovɔ to quīdenaɔ tinitatis y have be thougħt me synɔ that itt woll be thenɔ a bowte mydsomɔ.
The Early Modern English period, between the 15th and 17th centuries, had abbreviations like ye for Þe, used for the word the: "hence, by later misunderstanding, Ye Olde Tea Shoppe."
During the growth of philological linguistic theory in academic Britain, abbreviating became very fashionable. The use of abbreviation for the names of J. R. R. Tolkien and his friend C. S. Lewis, and other members of the Oxford literary group known as the Inklings, are sometimes cited as symptomatic of this. Likewise, a century earlier in Boston, a fad of abbreviation started that swept the United States, with the globally popular term OK generally credited as a remnant of its influence.
After World War II, the British greatly reduced the use of the full stop and other punctuation points after abbreviations in at least semi-formal writing, while the Americans more readily kept such use until more recently, and still maintain it more than Britons. The classic example, considered by their American counterparts quite curious, was the maintenance of the internal comma in a British organisation of secret agents called the "Special Operations, Executive"—"S.O.,E"—which is not found in histories written after about 1960.
But before that, many Britons were more scrupulous at maintaining the French form. In French, the period only follows an abbreviation if the last letter in the abbreviation is not the last letter of its antecedent: "M." is the abbreviation for "monsieur" while "Mme" is that for "madame". Like many other cross-channel linguistic acquisitions, many Britons readily took this up and followed this rule themselves, while the Americans took a simpler rule and applied it rigorously.
Over the years, however, the lack of convention in some style guides has made it difficult to determine which two-word abbreviations should be abbreviated with periods and which should not. The U.S. media tend to use periods in two-word abbreviations like United States (U.S.), but not personal computer (PC) or television (TV). Many British publications have gradually done away with the use of periods in abbreviations.
Minimization of punctuation in typewritten material became economically desirable in the 1960s and 1970s for the many users of carbon-film ribbons since a period or comma consumed the same length of non-reusable expensive ribbon as did a capital letter.
Widespread use of electronic communication through mobile phones and the Internet during the 1990s allowed for a marked rise in colloquial abbreviation. This was due largely to increasing popularity of textual communication services such as instant- and text messaging. SMS, for instance, supports message lengths of 160 characters at most (using the GSM 03.38 character set). This brevity gave rise to an informal abbreviation scheme sometimes called Textese, with which 10% or more of the words in a typical SMS message are abbreviated. More recently Twitter, a popular social networking service, began driving abbreviation use with 140 character message limits.
In modern English, there are several conventions for abbreviations, and the choice may be confusing. The only rule universally accepted is that one should be consistent, and to make this easier, publishers express their preferences in a style guide. Questions which arise include those in the following subsections.
If the original word was capitalized then the first letter of its abbreviation should retain the capital, for example Lev. for Leviticus. When a word is abbreviated to more than a single letter and was originally spelled with lower case letters then there is no need for capitalization. However, when abbreviating a phrase where only the first letter of each word is taken, then all letters should be capitalized, as in YTD for year-to-date, PCB for printed circuit board and FYI for for your information. However, see the following section regarding abbreviations that have become common vocabulary: these are no longer written with capital letters.
A period (full stop) is often used to signify an abbreviation, but opinion is divided as to when and if this should happen.
According to Hart's Rules, the traditional rule is that abbreviations (in the narrow sense that includes only words with the ending, and not the middle, dropped) terminate with a full stop, whereas contractions (in the sense of words missing a middle part) do not, but there are exceptions. Fowler's Modern English Usage says full stops are used to mark both abbreviations and contractions, but recommends against this practice: advising them only for abbreviations and lower-case initialisms and not for upper-case initialisms and contractions.
In American English, the period is usually included. In some cases periods are optional, as in either US or U.S. for United States, EU or E.U. for European Union, and UN or U.N. for United Nations. There are some house styles, however—American ones included—that remove the periods from almost all abbreviations. For example:The U.S. Manual on Uniform Traffic Control Devices advises that periods should not be used with abbreviations on road signs, except for cardinal directions as part of a destination name. (For example, "Northwest Blvd", "W. Jefferson", and "PED XING" all follow this recommendation.)
AMA style, used in many medical journals, uses no periods in abbreviations or acronyms, with almost no exceptions. Thus eg, ie, vs, et al., Dr, Mr, MRI, ICU, and hundreds of others contain no periods. The only exceptions are "No." (to avoid the appearance of "No"); initials within persons' names (such as "George R. Smith"); and "St." within persons' names when the person prefers it (such as "Emily R. St. Clair") (but not in city names such as St Louis or St Paul). (AMA style also forgoes italic on terms long since naturalized into English from Latin, New Latin, other languages, or ISV; thus, no italic for eg, ie, vs, et al., in vivo, in vitro, or in situ.)
Acronyms that were originally capitalized (with or without periods) but have since entered the vocabulary as generic words are no longer written with capital letters nor with any periods. Examples are sonar, radar, lidar, laser, snafu, and scuba.
Today, spaces are generally not used between single-letter abbreviations of words in the same phrase, so one almost never encounters "U. S."
When an abbreviation appears at the end of a sentence, only one period is used: The capital of the United States is Washington, D.C.
There is a question about how to pluralize abbreviations, particularly acronyms. Often a writer will add an 's' following an apostrophe, as in "PC's". However, this style is not preferred by many style guides. For instance, Kate Turabian, writing about style in academic writings, allows for an apostrophe to form plural acronyms "only when an abbreviation contains internal periods or both capital and lowercase letters". Turabian would therefore prefer "DVDs" and "URLs" and "Ph.D.'s", while the Modern Language Association explicitly says, "do not use an apostrophe to form the plural of an abbreviation". Also, the American Psychological Association specifically says, "without an apostrophe".
However, the 1999 style guide for the New York Times states that the addition of an apostrophe is necessary when pluralizing all abbreviations, preferring "PC's, TV's and VCR's".
Following those who would generally omit the apostrophe, to form the plural of run batted in, simply add an s to the end of RBI.RBIs
For all other rules, see below:
To form the plural of an abbreviation, a number, or a capital letter used as a noun, simply add a lowercase s to the end. Apostrophes following decades and single letters are also common.A group of MPs
The roaring 20s
Mind your Ps and Qs
To indicate the plural of the abbreviation or symbol of a unit of measure, the same form is used as in the singular.1 lb or 20 lb
1 ft or 16 ft
1 min or 45 min
When an abbreviation contains more than one full point, Hart's Rules recommends putting the s after the final one.Ph.D.s
However, subject to any house style or consistency requirement, the same plurals may be rendered less formally as:PhDs
the DTs. (This is the recommended form in the New Oxford Dictionary for Writers and Editors.)
According to Hart's Rules, an apostrophe may be used in rare cases where clarity calls for it, for example when letters or symbols are referred to as objects.The x's of the equation
Dot the i's and cross the t's
However, the apostrophe can be dispensed with if the items are set in italics or quotes:The xs of the equation
Dot the 'i's and cross the 't's
In Latin, and continuing to the derivative forms in European languages as well as English, single-letter abbreviations had the plural being a doubling of the letter for note-taking. Most of these deal with writing and publishing. A few longer abbreviations use this as well.
Publications based in the U.S. tend to follow the style guides of The Chicago Manual of Style and the Associated Press. The U.S. Government follows a style guide published by the U.S. Government Printing Office. The National Institute of Standards and Technology sets the style for abbreviations of units.
Many British publications follow some of these guidelines in abbreviation:For the sake of convenience, many British publications, including the BBC and The Guardian, have completely done away with the use of full stops or periods in all abbreviations. These include:
Social titles, like Ms or Mr (though these would usually not have had full stops—see above) Capt, Prof, etc.;
Two-letter abbreviations for countries ("US", not "U.S.");
Abbreviations beyond three letters (full caps for all except initialisms);
Words seldom abbreviated with lower case letters ("PR", instead of "p.r.", or "pr")
Names ("FW de Klerk", "GB Whiteley", "Park JS"). A notable exception is The Economist which writes "Mr F. W. de Klerk".
Scientific units (see Measurement below).
Acronyms are often referred to with only the first letter of the abbreviation capitalized. For instance, the North Atlantic Treaty Organisation can be abbreviated as "Nato" or "NATO", and Severe Acute Respiratory Syndrome as "Sars" or "SARS" (compare with "laser" which has made the full transition to an English word and is rarely capitalised at all).
Initialisms are always written in capitals; for example the "British Broadcasting Corporation" is abbreviated to "BBC", never "Bbc". An initialism is similar to acronym but is not pronounced as a word.
When abbreviating scientific units, no space is added between the number and unit (100mph, 100m, 10cm, 10°C). (This is contrary to the SI standard; see below.)
A doubled letter appears in abbreviations of some Welsh names, as in Welsh the double "l" is a separate sound: "Ll. George" for (British prime minister) David Lloyd George.
Some titles, such as "Reverend" and "Honourable", are spelt out when preceded by "the", rather than as "Rev." or "Hon." respectively. This is true for most British publications, and some in the United States.
A repeatedly used abbreviation should be spelt out for identification on its first occurrence in a written or spoken passage. Abbreviations likely to be unfamiliar to many readers should be avoided.
Writers often use shorthand to denote units of measure. Such shorthand can be an abbreviation, such as "in" for "inch" or can be a symbol such as "km" for "kilometre".
The shorthand "in" applies to English only—in Afrikaans for example, the shorthand "dm" is used for the equivalent Afrikaans word "duim". Since both "in" and "dm" are contractions of the same word, but in different languages, they are abbreviations. A symbol on the other hand, defined as "Mark or character taken as the conventional sign of some object or idea or process" applies the appropriate shorthand by substitution rather than by contraction. Since the shorthand for kilometre (quilômetro in Portuguese or χιλιόμετρο in Greek) is "km" in both languages and the letter "k" does not appear in the expansion of either translation, "km" is a symbol as it is a substitution rather than a contraction. It is a logogram rather than an abbreviation.
In the International System of Units (SI) manual the word "symbol" is used consistently to define the shorthand used to represent the various SI units of measure. The manual also defines the way in which units should be written, the principal rules being:The conventions for upper and lower case letters must be observed—for example 1 MW (megawatts) is equal to 1,000,000,000 mW (milliwatts).
No periods should be inserted between letters—for example "m.s" (which is an approximation of "m·s", which correctly uses middle dot) is the symbol for "metres multiplied by seconds", but "ms" is the symbol for milliseconds.
No periods should follow the symbol unless the syntax of the sentence demands otherwise (for example a full stop at the end of a sentence).
The singular and plural versions of the symbol are identical—not all languages use the letter "s" to denote a plural.
A syllabic abbreviation is usually formed from the initial syllables of several words, such as Interpol = International + police. It is a variant of the acronym. Syllabic abbreviations are usually written using lower case, sometimes starting with a capital letter, and are always pronounced as words rather than letter by letter. Syllabic abbreviations should be distinguished from portmanteaus, which combine two words without necessarily taking whole syllables from each.
Syllabic abbreviations are not widely used in English or French. The United States Navy, however, often uses syllabic abbreviations, as described below, and some UK government ministries such as Ofcom (Office of Communications) and Oftel (Office of Telecommunications) use this style.
On the other hand, they prevailed in Germany under the Nazis and in the Soviet Union for naming the plethora of new bureaucratic organisations. For example, Gestapo stands for Geheime Staats-Polizei, or "secret state police". Similarly, Leninist organisations such as the Comintern (Communist International) and Komsomol (Kommunisticheskii Soyuz Molodyozhi, or "Communist youth union") used Russian language syllabic abbreviations. This has given syllabic abbreviations negative connotations in some countries, (as in Orwell's Newspeak), notwithstanding that such abbreviations were used in Germany even before the Nazis came to power, e.g., Schupo for Schutzpolizei, and are still used, e.g. Kripo for Kriminalpolizei.
Syllabic abbreviations were also typical for the German language used in the German Democratic Republic, e.g. Stasi for Staatssicherheit ("state security", the secret police) or Vopo for Volkspolizist ("people's policeman"). Other uses are in company or product names such as Aldi, from the name of the founder, Theo Albrecht, and the German word Diskont (discount) or Haribo, from the name of the founder and the headquarters of the company, Hans Riegl Bonn.
Syllabic abbreviations are de rigueur in Spanish; examples abound in organization names such as Pemex for Petróleos Mexicanos ("Mexican Petroleums") or Fonafifo for Fondo Nacional de Financimiento Forestal (National Forestry Financing Fund).
East Asian languages whose writing systems use Chinese characters form abbreviations similarly by using key Chinese characters from a term or phrase. For example, in Japanese the term for the United Nations, kokusai rengō (国際連合) is often abbreviated to kokuren (国連). (Such abbreviations are called ryakugo (略語) in Japanese; see also Japanese abbreviated and contracted words). The syllabic abbreviation is frequently used for universities: for instance, Běidà (北大) for Běijīng Dàxué (北京大学, Peking University) and Tōdai (東大) for Tōkyō daigaku (東京大学, University of Tokyo). The English phrase "Gung ho" originated as a Chinese abbreviation.
Partially syllabic abbreviations are preferred by the US Navy, as it increases readability amidst the large number of initialisms that would otherwise have to fit into the same acronyms. Hence DESRON 6 is used (in the full capital form) to mean "Destroyer Squadron 6", while COMNAVAIRLANT would be "Commander, Naval Air Force (in the) Atlantic."