# Abbreviations include acronyms, initialisms, shortened words, and contractions. In most contexts, the technical distinction between acronyms and initialisms isn't relevant; it's fine to use the word *acronym* to refer to both. - An acronym is formed from the first letters of words in a phrase, but is pronounced as if it were a word itself: - *NATO* for *North Atlantic Treaty Organization* - *scuba* for *self-contained underwater breathing apparatus* - An initialism is also formed from the first letters of words in a phrase, but each letter is pronounced separately: - *CIA* for *Central Intelligence Agency* - *FYI* for *For Your Information* - *PR* for *Public Relations* - A shortened word is just part of a word or phrase, sometimes with a period at the end: - *Dr.* for *doctor* - *etc.* for *et cetera* - *min* for *minutes* - *CA* for *California* - [Contractions](https://developers.google.com/style/contractions) are discussed in a separate page of this style guide. ## Long and short versions of a word Some words have a long version and a short version---for example: - *application* and *app* - *demonstration* and *demo* - *synchronize* and *sync* The short versions of the words are not abbreviations, and if you use them, you don't need to put a period after them. If you're not sure whether a word is an abbreviation or just a short version of a longer word, look in our list of [resources](https://developers.google.com/style#editorial-resources). If that doesn't settle the issue, use the speaking test: if you speak the short version as a word (*This is a demo version of the product*), you can usually treat it as a word and not an abbreviation. ## When to use abbreviations Abbreviations are intended to save the writer and the reader time. If the reader has to think about an abbreviation, it can slow down their reading comprehension. ### General dos and don'ts - Use standard acronyms and initialisms that will save the reader time. - Spell out abbreviations on first reference. For more information, see [When to spell out a term](https://developers.google.com/style/abbreviations#spelling-out). - Avoid using abbreviations for terms that aren't related to the main topic of the document. - In the following examples, the main topic of the document is the internet of things, so *low Earth orbit* should not be abbreviated. - Recommended: The internet of things (IoT) service can even be used for connecting to sensors in low Earth orbit. - Not recommended: The IoT (internet of things) service can even be used for connecting to sensors in LEO (low Earth orbit). - Be wary of using specialized abbreviations that your readers might not understand. For more information about when to use such language, see [Jargon](https://developers.google.com/style/jargon). ## When to spell out a term In general, when an abbreviation is likely to be unfamiliar to the audience, spell it out upon first mention and include the abbreviation in parentheses immediately following. Recommended: * Border Gateway Protocol* (*BGP*) For all subsequent mentions of the abbreviation, use the abbreviation by itself. If you use an abbreviation only once, include it only if you think the abbreviation is as commonly used as the spelled-out term. Otherwise, don't include the abbreviation. If the first mention of a term occurs in a [heading or title](https://developers.google.com/style/headings), you can use the abbreviation and then spell out the abbreviation in the first paragraph that follows the heading or title. When deciding to spell out a term, consider your audience. If your document is going to be translated, spelling out a term can provide important context for both human and machine translation. It can also be helpful for readers who aren't as familiar with English. If the majority of your audience is likely to recognize and understand the term, then you don't need to spell it out. For example, if you're writing documentation for developers that references an API, you don't need to spell out *application programming interface*. However, if you're explaining the general concept of an API to someone with no programming experience, spelling out the abbreviation can be helpful. In some cases, spelling out a term doesn't help the reader understand the term. For example, writing out *portable document format* doesn't help the reader understand what a *PDF* document is. In those cases, don't spell out the term. The following abbreviations rarely need to be spelled out: - AI - API - DVD - File formats such as PDF or XML - HTML - PC - RAM - REST - [Units of measurement](https://developers.google.com/style/units-of-measure#byte-units) such as MB, MiB, GB, or GiB - URL - USB ### Format abbreviation introductions When you spell out a term and include its abbreviation in parentheses, do the following: - Italicize both the spelled-out term and its abbreviation. - In the following examples, the only difference is the italicization of *BGP*: - Recommended: Establish *Border Gateway Protocol* (*BGP*) sessions using a router on the peer network. - Not recommended: Establish *Border Gateway Protocol* (BGP) sessions using a router on the peer network. - Capitalize the spelled-out version of the abbreviation only if the long form is a proper noun or is conventionally capitalized. - That is, don't capitalize the term only because the abbreviation includes capital letters. - Recommended: data manipulation language (DML) - Not recommended: Data Manipulation Language (DML) - Include the abbreviation in [link text](https://developers.google.com/style/cross-references#abbreviations). ## Abbreviations not to use Don't use *i.e.* or *e.g.*; instead, use *that is* or *for example*, respectively. For more information, see [e.g.](https://developers.google.com/style/word-list#eg) and [i.e.](https://developers.google.com/style/word-list#ie) It's [okay to use *etc.* in some circumstances](https://developers.google.com/style/word-list#etc), but it's best to use different phrasing in most lists. For more information, see [Comma-separated lists](https://developers.google.com/style/lists#comma-separated-lists). Don't use internet slang abbreviations such as [*tl;dr*](https://developers.google.com/style/word-list#tldr), [*ymmv*](https://developers.google.com/style/word-list#ymmv), [*RTFM*](https://developers.google.com/style/word-list#rtfm), or others. Write out what you mean in a non-figurative way. Use the most common form of a word. If the spelled-out word is common and easily understandable, use that rather than abbreviating. For example, write *approximately* instead of *approx.* Spell out shortened words or common symbols that are substitutions for words. Recommended: Updating the software made throughput 10 times faster. Not recommended: Updating the software made throughput 10x faster. ## Periods with abbreviations Follow these guidelines: - Don't use periods with acronyms or initialisms. - Put a period at the end of a shortened word, except for [date and time](https://developers.google.com/style/dates) abbreviations. - If you write or say an abbreviation as a word (for example, *app* or *sync*), don't put a period after it. - Don't use a period with an abbreviation for the name of a country, US state, or the District of Columbia (DC). ## Plural abbreviations For guidance about how to make abbreviations plural, see [Pluralization](https://developers.google.com/style/pluralization#making-abbreviations-plural). ## Abbreviations as verbs Don't use acronyms, initialisms, or shortened words as verbs. Recommended: Use SSH to log in to your remote shell. Not recommended: Then ssh into your remote shell. ## Indefinite articles before abbreviations Whether to use *a* or *an* before a term depends on the pronunciation of the term: use *a* before any consonant sound and *an* before any vowel sound. Pronunciation of abbreviations can vary, so in general, base your decision on the pronunciation that's most common for your audience. In particular, our word list includes preferences for "[a SQL](https://developers.google.com/style/word-list#sql)", "[a FHIR](https://developers.google.com/style/word-list#fhir)", and "[an SAP](https://developers.google.com/style/word-list#sap)". For more information about articles, see [Articles](https://developers.google.com/style/articles).