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1 Usage

Abbreviations have been used since ancient times (see Palaeography and Diplomatic). A distinction is observed between abbreviations and the contractions that are frequently used in old manuscripts and early printed books whereby letters are omitted, or particular groups of letters are represented by somewhat arbitrary symbols. The commonest form of abbreviation is when an initial letter is used to indicate the whole word; but often other letters are added. In some languages, letters are doubled to indicate a plural or a superlative.

2 Style conventions

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 this end publishers express their preferences in a style guide.

Questions which arise include the following:

• Use of upper or lower case letters. If the original word was capitalised, then the first letter of its abbreviation should retain the capital, e.g., Lev. for Leviticus. When abbreviating words spelt with lower case letters, there is no consistent rule.
• Use of periods (full stops) and spaces, e.g. when abbreviating United States, should one write US, U.S. or U. S.? In American English the period is usually added if the abbreviation may be interpreted as a word, though some American writers do not use a period here. There is no stop/period between letters of the same word, e.g., St. and not S.t. for Saint.
• Many British publications and websites (notably the BBC) follow these guidelines:
  • If the abbreviation retains the last letter of the original (as, for example "Mister"), the period is not included: Mr John Smith.
  • If the abbreviation does not have the last letter of the original, the period is included. "exempli gratia" is abbreviated as "e.g." (though many British writers would use "eg").
  • If used to refer to a country or a group like the United States or United Nations, the period is not included: US and UN respectively.
  • Acronyms are sometimes referred to with only the first letter of the abbreviation capitalised. For instance, the North Atlantic Treaty Organization can be abbreviated as Nato, and Severe Acute Respiratory Syndrome as Sars. Initialisms (which are similar to acronyms but which are not pronounced as words) are always written in capitals, for instance the British Broadcasting Corporation is abbreviated to BBC, never Bbc.
• Plurals are often formed by doubling up the last letter of the abbreviation: MS=manuscript, MSS=manuscripts; p=page, pp=pages; s=section, ss=sections)
• Whether to add an apostrophe for a plural where the plural is not formed by doubling up the last letter: should one write CDs or CD's? The apostrophe is not needed grammatically but sometimes is added to make it clear that the s is not part of the abbreviation.

In East Asian languages which use Chinese ideograms instead of an alphabet, abbreviations are similarly formed by using key characters instead of letters. For example, in Japanese the term for the United Nations, kokusai rengo (国際連合) is often abbreviated to kokuren (国連).

3 Examples

• List of classical abbreviations
• List of mediaeval abbreviationsOf the different kinds of abbreviations in use in the middle ages; the following are examples: A. Ave Maria. Beatus Paulus, Beatus Petrus. Carissimus (also plur. Carissimi , Clarissimus, Circum. Deus, Dominicus, Dux. Dominus hoster Papa. Felicissimus, Fra
• List of abbreviations in use in 1911Based on a British encyclopaedia published in 1911, this is a list of abbreviations in use at the time. The import of these will often be readily understood from the context in which they occur. There is no occasion to explain here the common abbreviation
• List of acronyms and initialismsThis is a list of acronyms, initialisms and pseudo-blends. For the purposes of this list, an acronym is an abbreviation that is pronounced as a series of constituent letters; an initialism is an abbreviation whose pronunciation is wholly or partly the nam