Provide the full form of an abbreviation at first use, unless the term usually appears in its abbreviated form (like USA, UK, PhD, CEO, FAQ) or is listed as a noun in the dictionary (e.g., DNA, GPS, TV).
In formal writing, abbreviations are not generally used to start a sentence.
- Poor: UFDs save lives.
Better: Unidentified floating devices save lives.
But acronyms (abbreviations pronounced as words) and contractions (like Dr. and Mr.) are acceptable at the start of a sentence.
- Correct: NATO was formed in 1949.
- Correct: Mr. Mittens is a most respectable cat.
Initialisms and acronyms are usually written in all capital letters, although abbreviated Latin terms often contain lowercase letters, as do scientific and technical abbreviations. Contractions of titles and proper nouns are capitalized.
- USA, UK, EU, UN, NATO, CEO, TBD, FYI, GPS, DNA
- e.g., i.e., etc., ibid., et al.
- ppm, mph, rpm, fp, ml, km, kg, dc, Hz, wt
- Mr., Dr., Rev., Pres., Sen., Gov., Gen., Sgt., Jan., Sun.
Also note that in most styles, abbreviations with two or more capital letters usually don’t require periods, but those ending in a lowercase letter do (except scientific abbreviations and abbreviated SI units).
Pluralize abbreviations by adding s or es without an apostrophe.
- SMSs (or SMSes)
- Drs. Who and Strange
Whether to use a or an before an abbreviation depends upon how it would be pronounced.
- a US senator, a PTA meeting
- an ATM, an MBA degree
What is an abbreviation?
An abbreviation is the shortened form of a term. It can be formed using the first letters of the words in a multi-word, or it may simply be the shortened form of a single word.
When to abbreviate a term
Abbreviate a term only if it appears multiple times in a document (at least three, but usually five times). Abbreviations are useful when space is limited. You can also use them to avoid repeating long phrases in a document, thus making it more readable.
- Poor: The National Aeronautics and Space Administration was set up in 1958. It is responsible for the United States’ civilian space program. Since its inception, the National Aeronautics and Space Administration has led the Apollo missions and launched the Skylab space station. The National Aeronautics and Space Administration also supports the International Space Station.
- Better: The National Aeronautics and Space Administration (NASA) was set up in 1958. It is responsible for the United States’ civilian space program. Since its inception, NASA has led the Apollo missions and launched the Skylab space station. NASA also supports the International Space Station.
Don’t try to abbreviate every single term in a document. Too many abbreviations can render a text unreadable.
- Poor: NASA is the US CSP. Since its inception, it has led the AMs and launched the SSS. NASA also supports the ISS.
Better: NASA is the United States’ civilian space program. It has led the Apollo missions and launched the Skylab space station. NASA also supports the International Space Station.
Nonstandard abbreviations are confined to tables, graphs, and figures, except in scientific and technical writing. Avoid using nonstandard abbreviations in headings; you want the reader to easily skim the document or just its table of contents. Also avoid the use of abbreviations in captions of figures and tables, which are considered reproducible and thus standalone.
In academic papers and business reports, provide a glossary or list of abbreviations after the table of contents to help the general reader.
Providing the full form
In general, explain an abbreviation by providing its full form at first use in a document.
- In urban areas, a small green space (SGS) can become a habitat for local species of birds.
- NATO (North Atlantic Treaty Organization) is a military alliance of 30 countries.
- The GDPR (General Data Protection Regulation) is one of the toughest privacy laws in the world.
- The National Aeronautics and Space Administration, better known as NASA, has released its latest climate assessment.
- Nongovernmental organizations, or NGOs, fill this gap.
Don’t capitalize the words in the full form of an abbreviation unless it is a proper noun.
- CPR: cardiopulmonary resuscitation
- TIN: tax identification number
- FBI: Federal Bureau of Investigation
- UK: United Kingdom
If a term usually appears in its abbreviated rather than complete form, the abbreviation need not be explained.
You also don’t need to provide the full form of an abbreviation listed as a noun rather than an abbreviation in standard dictionaries (like Merriam-Webster).
Avoid redundancies like “SSN number.” SSN stands for “social security number,” making the word number after the abbreviation redundant.
Use of capital letters
Abbreviations that are initialisms or acronyms, formed using the initial letters of the words of a phrase, generally comprise all capital letters.
- FAQ: frequently asked question
- PC: personal computer
- NAFTA: North American Free Trade Agreement
- BA: Bachelor of Arts
- BC: before Christ
Contractions usually appear in lowercase letters, but those that appear before a name as titles or are part of aare capitalized (the first letter of the contraction is then a capital letter).
- abbr.: abbreviation
- vol.: volume
- ed.: editor/edited
- Dr.: Doctor
- Gen.: General
- Prof.: Professor
- estd.: established
- Inc.: Incorporated
Technical and scientific abbreviations comprising the initial letters of a term may contain lowercase letters. Abbreviatedare also not capitalized.
- rpm: revolutions per minute
- bhp: brake horsepower
- mph: miles per hour
- km: kilometer
- GlcNAc: N-acetylglucosamine
Latin abbreviations are also generally lowercased.
- e.g.: exempli gratia (“for the sake of example”)
- i.e.: id est (“that is”)
- ibid.: ibidem (“in the same place”)
- etc.: et cetera (“and the rest”)
- et al.: et alii (“and others”)
In academic and other formal writing, abbreviations likeand i.e. are not generally used in running text but in , figures, tables, and citations.
Use of periods
In general, abbreviations with at least two capital letters contain no period.
Abbreviations that end in lowercase letters often contain periods.
Note that periods are omitted in scientific and technical abbreviations, abbreviated SI units, and abbreviations containing the preposition per.
Contractions and other shortened forms that end in a lowercase letter usually take a period.
Inusage, a period (or full stop) is used only if the shortened form comprises the first few letters or the first syllable of the word, but not otherwise. Thus, the contraction Dr (for Doctor) does not take a period, but one does appear after Jan. (for January).
Use of a/an and the
Use thea or an before an abbreviation depending upon how it is read aloud. If it starts with a consonant sound, use a; otherwise, use an.
- a DVD player
- an IQ test
- pronounced “a yoo-en resolution”
a UN resolution
- a UFO
- pronounced “an en-bee-ay” game
an NBA game
- an HR professional
With acronyms (abbreviations pronounced as words), the article the is omitted, even when it would be used with the full form.
- The but
TheOPEC is a cartel of 13 countries.
Organization of the Petroleum Exporting Countries is a cartel of 13 countries.
But with initialisms (in which the individual letters are pronounced), use the with the abbreviation if it is used with the full form.
- The orThe UK is an island nation that is part of Europe.
United Kingdom is an island nation that is part of Europe.
At the start of a sentence
In formal writing, avoid starting awith an abbreviation. Use the full form instead, or rephrase.
- Poor: UN representatives met in Brussels today.
Better: United Nations representatives met in Brussels today.
- Poor: UK health officials are now recommending a booster dose.
Better: Health officials in the UK are now recommending a booster dose.
Because acronyms and contractions are read aloud as words, they are acceptable at the beginning of a sentence.
- Correct: Dr. Green has ordered additional tests.
- Correct: NATO officials met with Kuwaiti diplomats in Brussels today.
Acronyms are abbreviations pronounced as words. Thus, NATO and NASA are acronyms, while USA and UK are initialisms.
If using the full form makes the sentence awkward, use the abbreviated form—for example, to refer to company names.
- Correct: UBS/
The Union Bank of Switzerlandopened a new office today in London.
- Correct: HSBC/
The Hong Kong and Shanghai Banking Corporationoperates in many countries in Asia.
To form the plural of an abbreviation, simply add s. An apostrophe is not incorrect but unnecessary and generally omitted in formal writing.
Abbreviations that already end in S can be pluralized either by adding another s or by adding es (SMSs or SMSes).
To form the plural of a contraction, add s and place a period after.
- Vols. 1–5
- Remiramen Femy and Minerva Dash, eds.
- Drs. Femy and Dash
The plurals of Mr. and Ms. are Messrs. and Mss. (or Mses.), seen only in formal usage.