ASAP, e.g., UNESCO, Dr, don't. Learn what common abbreviations mean, the difference between initialisms and acronyms, and the rules for using them correctly.
ASAP, e.g., UNESCO, Dr, don't, exam. Abbreviations are everywhere: in letters, news, textbooks, signs and messages. Used correctly, they save time and space. Used wrongly, they confuse readers and lose marks. This guide explains the different kinds of abbreviation, the rules for punctuation, capital letters and plurals, and gives 212 common abbreviations with their full forms.
Its main part is organised by type: Latin abbreviations, titles and everyday abbreviations, units of measurement, initialisms, acronyms, text abbreviations, contractions and clipped words. It also covers common mistakes, popular myths about acronyms, key points, ten practice questions and a teacher activity.
It connects with Parts of Speech, Formal vs. Informal English, Punctuation Rules and Common Errors in English. Spelling in this guide follows British English.
An abbreviation is a shortened form of a word or phrase. The word comes from the Latin abbreviare, meaning "to shorten". There are several kinds, and the difference between them matters for punctuation and pronunciation.
| Type | What it is | Examples |
|---|---|---|
| Abbreviation | A shortened word, often ending with a full stop in some styles | Prof., approx., Jan. |
| Initialism | Initial letters, each said separately | BBC, UN, CEO, MP |
| Acronym | Initial letters, pronounced as a word | NASA, UNESCO, NATO, laser |
| Contraction | A word or words shortened by leaving out letters, shown with an apostrophe | can't, I'm, o'clock |
| Clipped word | A word cut short in everyday speech | exam, gym, photo, flu |
| Blend (portmanteau) | Two words joined, with parts of each | brunch (breakfast + lunch), smog (smoke + fog) |
Some acronyms have become ordinary words and are written in lower case: radar, laser, scuba and sonar.
| Rule | Explanation and example |
|---|---|
| Write in full the first time | Give the full form with the abbreviation in brackets: the World Health Organization (WHO). Use the short form afterwards. |
| Full stops (British style) | No full stop when the last letter of the word is included: Mr, Mrs, Dr, St, Ltd. Use a full stop when the word is cut short: Prof., Capt., approx. |
| Full stops (American style) | American English usually uses a full stop after titles: Mr., Mrs., Dr. |
| No full stops in initialisms and acronyms | BBC, UN, NASA, MP (older style used B.B.C.) |
| Capital letters | Initialisms and acronyms of names are usually capitals: UNICEF. Common-word acronyms are lower case: radar, laser. |
| Plurals | Add -s without an apostrophe: CDs, MPs, PhDs. Units do not change: 5 km, 10 kg. |
| a or an | Choose by sound, not by spelling: an MP (em-pee), an SOS, a UN official (you-en), a UNESCO report. |
| Avoid in formal writing | Write for example and and so on in essays, and avoid text abbreviations such as BTW and LOL. |
| Do not start a sentence with a symbol or most abbreviations | Write Doctor Khan arrived, or Dr Khan arrived, but not e.g. fruit at the start. |
Latin abbreviations are common in academic writing. In sentences, use a comma after e.g. and i.e. in American style; British style often omits the comma. Do not write and etc., because et already means "and".
| Abbreviation | Full form | Meaning or use |
|---|---|---|
| e.g. | exempli gratia | for example |
| i.e. | id est | that is; in other words |
| etc. | et cetera | and so on |
| et al. | et alii | and others (in references) |
| viz. | videlicet | namely |
| cf. | confer | compare |
| N.B. | nota bene | note well |
| P.S. | post scriptum | a note added after a letter |
| a.m. | ante meridiem | before noon |
| p.m. | post meridiem | after noon |
| ibid. | ibidem | in the same place (in references) |
| op. cit. | opere citato | in the work already cited |
| vs. or v. | versus | against |
| c. or ca. | circa | about (used with dates) |
| A.D. | anno Domini | in the year of the Lord (after the birth of Christ) |
| Q.E.D. | quod erat demonstrandum | which was to be proved |
| R.I.P. | requiescat in pace | may he or she rest in peace |
| CV | curriculum vitae | a summary of education and work |
| per cent | per centum | out of a hundred |
| ad lib. | ad libitum | as one pleases; unprepared |
| M.O. | modus operandi | method of working |
| No. | numero | number |
| Abbreviation | Full form | Meaning or use |
|---|---|---|
| Mr | Mister | title for a man |
| Mrs | Mistress (old form) | title for a married woman |
| Ms | no marriage reference | title for any woman |
| Dr | Doctor | medical or academic title |
| Prof. | Professor | university teacher |
| Capt. | Captain | military or ship rank |
| Col. | Colonel | military rank |
| Gen. | General | military rank |
| Sgt | Sergeant | rank |
| Rev. | Reverend | title for clergy |
| Hon. | Honourable | title of respect |
| Jr | Junior | son with his father's name |
| Sr | Senior | father with the same name |
| St | Saint or Street | name of a saint or road |
| Rd | Road | used in addresses |
| Ave. | Avenue | used in addresses |
| Mt | Mount | mountain |
| Dept | Department | part of an organisation |
| Govt | Government | rulers of a country |
| Ltd | Limited | company with limited liability |
| Co. | Company | business |
| Inc. | Incorporated | American company |
| approx. | approximately | about |
| est. | established or estimated | date or guess |
| misc. | miscellaneous | mixed |
| tel. | telephone | used in letters |
| ext. | extension | phone extension |
| enc. | enclosure | attached to a letter |
| cc | carbon copy | copy of an email or letter |
| bcc | blind carbon copy | hidden copy |
| RSVP | répondez s'il vous plaît | please reply |
| ASAP | as soon as possible | urgently |
| ETA | estimated time of arrival | expected arrival |
| FYI | for your information | for your notice |
| TBA | to be announced | not yet decided |
| TBC | to be confirmed | not yet certain |
| DIY | do it yourself | home repair |
| VIP | very important person | special guest |
| PTO | please turn over | continued on the back |
| a.k.a. | also known as | alternative name |
Unit abbreviations take no full stop and no plural -s: 5 km, not 5 kms.
| Abbreviation | Full form |
|---|---|
| km | kilometre |
| m | metre |
| cm | centimetre |
| mm | millimetre |
| kg | kilogram |
| g | gram |
| mg | milligram |
| l | litre |
| ml | millilitre |
| mph | miles per hour |
| km/h | kilometres per hour |
| °C | degrees Celsius |
| °F | degrees Fahrenheit |
| hr | hour |
| min | minute |
| sec | second |
| ft | foot or feet |
| in. | inch |
| yd | yard |
| lb | pound (weight) |
| oz | ounce |
| sq. | square |
| cu. | cubic |
| hp | horsepower |
These abbreviations are said by naming each letter, for example "B-B-C".
| Abbreviation | Full form |
|---|---|
| UN | United Nations |
| UK | United Kingdom |
| USA | United States of America |
| UAE | United Arab Emirates |
| EU | European Union |
| WHO | World Health Organization |
| IMF | International Monetary Fund |
| WTO | World Trade Organization |
| ICC | International Cricket Council |
| IOC | International Olympic Committee |
| OIC | Organisation of Islamic Cooperation |
| BBC | British Broadcasting Corporation |
| CNN | Cable News Network |
| FBI | Federal Bureau of Investigation |
| CIA | Central Intelligence Agency |
| GDP | gross domestic product |
| CEO | chief executive officer |
| MP | Member of Parliament |
| PM | Prime Minister |
| HR | human resources |
| IT | information technology |
| PC | personal computer |
| TV | television |
| DVD | digital versatile disc |
| CD | compact disc |
| USB | Universal Serial Bus |
| Portable Document Format | |
| URL | Uniform Resource Locator |
| HTML | HyperText Markup Language |
| WWW | World Wide Web |
| ISP | Internet service provider |
| GPS | Global Positioning System |
| SMS | short message service |
| ATM | automated teller machine |
| PIN | personal identification number |
| VAT | value added tax |
| ID | identification |
| DNA | deoxyribonucleic acid |
| RNA | ribonucleic acid |
| HIV | human immunodeficiency virus |
| ECG | electrocardiogram |
| MRI | magnetic resonance imaging |
| ICU | intensive care unit |
| OPD | outpatient department |
| GMT | Greenwich Mean Time |
| AI | artificial intelligence |
| FAQ | frequently asked questions |
| ISBN | International Standard Book Number |
| MCQ | multiple-choice question |
These abbreviations are said as words, for example "NASA" rhymes with Casa.
| Abbreviation | Full form |
|---|---|
| NASA | National Aeronautics and Space Administration |
| UNESCO | United Nations Educational, Scientific and Cultural Organization |
| UNICEF | United Nations Children's Fund (originally the International Children's Emergency Fund) |
| NATO | North Atlantic Treaty Organization |
| OPEC | Organization of the Petroleum Exporting Countries |
| SAARC | South Asian Association for Regional Cooperation |
| ASEAN | Association of Southeast Asian Nations |
| FIFA | Fédération Internationale de Football Association |
| radar | radio detection and ranging |
| laser | light amplification by stimulated emission of radiation |
| scuba | self-contained underwater breathing apparatus |
| sonar | sound navigation and ranging |
| AIDS | acquired immune deficiency syndrome |
| SWAT | Special Weapons and Tactics |
| AWOL | absent without leave |
| GIF | Graphics Interchange Format |
| JPEG | Joint Photographic Experts Group |
| ROM | read-only memory |
| RAM | random-access memory |
| BASIC | Beginners' All-purpose Symbolic Instruction Code |
| TOEFL | Test of English as a Foreign Language |
| IELTS | International English Language Testing System |
| CAPTCHA | Completely Automated Public Turing test to tell Computers and Humans Apart |
These are used in text messages and casual chat. Do not use them in essays, applications or formal emails.
| Abbreviation | Full form |
|---|---|
| BTW | by the way |
| LOL | laughing out loud |
| OMG | oh my God |
| BRB | be right back |
| IMO | in my opinion |
| TBH | to be honest |
| DM | direct message |
| AFAIK | as far as I know |
| IDK | I do not know |
| TTYL | talk to you later |
| THX | thanks |
| PLS | please |
| NP | no problem |
Contractions are used in speech and informal writing. In formal writing, write the full form.
| Abbreviation | Full form |
|---|---|
| don't | do not |
| doesn't | does not |
| can't | cannot |
| won't | will not (an irregular contraction) |
| shan't | shall not |
| isn't | is not |
| aren't | are not |
| I'm | I am |
| you're | you are |
| he's | he is or he has |
| she'll | she will |
| we've | we have |
| they'd | they would or they had |
| it's | it is or it has |
| let's | let us |
| who's | who is or who has |
| there's | there is |
| could've | could have |
| o'clock | of the clock |
| ma'am | madam |
Clipped words are common in everyday speech. Many, such as exam, photo and phone, are now accepted in standard writing.
| Abbreviation | Full form |
|---|---|
| ad | advertisement |
| exam | examination |
| gym | gymnasium |
| lab | laboratory |
| maths | mathematics |
| phone | telephone |
| photo | photograph |
| plane | aeroplane |
| fridge | refrigerator |
| flu | influenza |
| bus | omnibus |
| pub | public house |
| zoo | zoological garden |
| vet | veterinary surgeon |
| memo | memorandum |
| info | information |
| app | application |
| demo | demonstration |
| bike | bicycle |
| mic | microphone |
| taxi | taximeter cab |
| Abbreviation | Use it to | Example |
|---|---|---|
| e.g. | give one or more examples | Bring stationery, e.g. pens and rulers. |
| i.e. | explain or restate | Bring a blue pen, i.e. not a black one. |
| etc. | show that a list continues | Bring pens, pencils, rulers, etc. |
| et al. | show that there are other authors | Smith et al. (2020) |
| a.m. / p.m. | show time before or after noon | The class starts at 9 a.m. |
| A.D. / B.C. | date years from the birth of Christ | The fort was built in A.D. 1100. |
A helpful trick: e.g. means "example given", and i.e. means "in essence".
Many popular stories claim that common words began as acronyms. Most of these stories are myths.
| Word | The myth | The truth |
|---|---|---|
| SOS | It means "Save Our Souls". | The letters were chosen because the Morse code pattern was simple to send and recognise. They do not stand for anything. |
| news | It means North, East, West, South. | It is simply the plural of new. |
| tip | It means "to insure promptness". | The origin is not an acronym. |
| posh | It means "port out, starboard home". | There is no good evidence for this story. |
| OK | It has a single agreed meaning. | Its origin is debated; many dictionaries trace it to a joking misspelling in nineteenth-century America. |
| Mistake | Correct | Why |
|---|---|---|
| and etc. | etc. | Et already means "and". |
| ATM machine | ATM | The M already stands for machine. |
| PIN number | PIN | The N already stands for number. |
| HIV virus | HIV | The V already stands for virus. |
| RSVP please | RSVP | It already means "please reply". |
| 5 kms | 5 km | Unit abbreviations do not take -s. |
| CD's | CDs | Do not use an apostrophe for a plural. |
| a MP, an UN official | an MP, a UN official | Choose a or an by sound. |
| Mr. Khan (in British style) | Mr Khan | No full stop when the last letter is included. |
| using i.e. for a list of examples | use e.g. | i.e. explains; e.g. gives examples. |
| writing BTW in an essay | by the way, or leave it out | Text abbreviations are informal. |
| its/it's confusion | its (belonging), it's (it is) | An apostrophe shows a contraction. |
Activity: give students a list of ten abbreviations from the tables and ask them to write the full form from memory, then to use each correctly in a sentence. A matching game with abbreviation cards and full-form cards works well. For older students, ask them to find five abbreviations in a news article and to explain whether each is an initialism or an acronym.
Please note: this guide uses British style for punctuation. Some abbreviations are written differently in other countries, and new ones appear all the time, so students should check a dictionary or style guide when in doubt.
10 questions. Select an answer for each, then submit to see your score instantly.