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Initialisms and acronyms

An initialism is an abbreviation made from the initials of a phrase. For example, AR (augmented reality), VFX (visual effects), DLC (downloadable content). An acronym is an initialism that is pronounced as a single word. For example, HUD (heads-up display), SONAR (sound navigation and ranging) Unity MARS (Mixed and Augmented Reality Studio).

Define initialisms and acronyms the first time you use them on each page. The exceptions to this rule are names of organizations or companies such as NASA or IBM, or abbreviations that are widely known, such as FAQ, URL, and USB. If the initialism or acronym appears in the Merriam-Webster dictionary, you don't need to define it on first use.


When you spell out an initialism or acronym, don’t capitalize the letters that make up the abbreviation unless the abbreviation is a proper noun or contains proper nouns.

Unity provides a Software Development Kit (SDK)...Unity provides a software development kit (SDK)...
Generate a map using Simultaneous Localization And Mapping (SLAM)Generate a map using simultaneous localization and mapping (SLAM)
Use the High Definition Render Pipeline (HDRP) to create high-fidelity visuals in your project.

Page titles and headings

Follow these best practices for using initialisms and acronyms in titles:

  • Avoid using abbreviations for the first time in a title or heading whenever possible. Some common or industry-recognized abbreviations are acceptable. Spell out any proprietary terms.
  • Don’t define an abbreviation within a title or heading. Specifically, don’t write out the abbreviation in full and then place the abbreviation in parentheses next to it. Use either the full term or the abbreviation.
  • Within a section hierarchy in the table of contents, use the full, non-abbreviated term in the title of the top-level topic in the hierarchy. For subsequent levels within the hierarchy, you can use the abbreviation in topic titles.
  • If the first use of an abbreviation (spelled out or abbreviated) is in a title or heading, introduce the term in the body text by spelling out the term and placing the initialism or acronym in parentheses.
Generate a map using SLAMGenerate a map using simultaneous localization and mapping
Get started with UI (User Interface) designGet started with user interface design


Unless an acronym refers to a person or an organization, don't use the possessive form.

The HUD's brightness

The HUD brightness

The brightness of the HUD

Unity MAR's featuresUnity MARS features
The CEO's email


Add a lowercase "s" to initialisms, acronyms, and other abbreviations when making them plural. Don’t add an apostrophe before the "s." For example, APIs, SDKs, IDEs.


In linguistics, an article is a word like "the," "a," or "an."

As a general rule, use an article when you use an initialism that is a noun. For example, "the FAQ," "the URL," "a HUD," "the USA." At Unity, the product names HDRP and URP are exceptions to this rule. Usage is sometimes different for the names of companies, universities, and other institutions. For example, IBM, UEA, UCL, and NASA don't have articles.

Whether to use "a" or "an" with an initialism or acronym depends on its pronunciation. Use "a" before a consonant sound. Use "an" before a vowel sound.


  • an HDR display
  • an HTML file
  • a DLL
  • a USB port
  • an ISP

Some initialisms can also be acronyms, which can change the article you must use, for example:

  • "A SQL database" (acronym) vs "an SQL database" (initialism)
  • "A FAQ page" (acronym) vs "an FAQ page" (initialism)

In these cases, use the article that corresponds to the most common pronounciation of the term.


Don't use periods with initialisms or acronyms, including the following types of abbreviations:

  • Date or time abbreviations
  • Abbreviations written as a word, such as "app" or "sync"
  • File types or formats, such as "GIF" or "XML"
  • Abbreviations for the name of a country, state, or province
  • Currency codes