WCAG 3.1.3 Unusual Words: Make Jargon and Idioms Accessible

Last updated: 2026-04-01

Level AAA Understandable WCAG 3.1.3

What This Criterion Requires

WCAG 3.1.3 requires a mechanism for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon. When content uses technical terminology, domain-specific jargon, colloquial expressions, or words with specialized meanings that differ from their common definition, users must be able to access a clear definition. This can be accomplished through inline definitions, glossary links, the HTML dfn element, or a dedicated glossary page. The criterion recognizes that language barriers are a significant accessibility concern, particularly for people with cognitive disabilities, learning disabilities, or those reading in a second language. Even highly literate users may struggle with unfamiliar specialized vocabulary. By providing clear definitions, content creators make their material more inclusive and easier to understand for the broadest possible audience, including non-native speakers, newcomers to a field, and people with varying levels of education or domain expertise.

Why It Matters

Unusual words, idioms, and jargon create comprehension barriers for a wide range of users. People with cognitive or learning disabilities may struggle to understand figurative language, technical terms, or words used in non-standard ways. Non-native speakers often cannot interpret idioms or culturally specific expressions. Screen reader users cannot easily look up a word in context the way a sighted user might hover over or right-click a term. Even experts in one field may be unfamiliar with jargon from another domain. Legal, medical, financial, and technical content frequently uses specialized vocabulary that excludes general audiences. Without definitions, users may misinterpret critical information, abandon content out of frustration, or make incorrect decisions based on misunderstood terminology. Providing definitions improves comprehension for everyone, reduces support requests, and demonstrates respect for the diverse backgrounds of your audience. It also benefits SEO, as search engines can better understand and index well-defined content.

Common Failures and How to Fix Them

Technical jargon without definitions

Content uses specialized technical terms without providing definitions, explanations, or links to a glossary, leaving non-expert readers unable to understand the material.

Inaccessible 
<p>The application uses a RESTful API with OAuth 2.0
  PKCE flow for authentication and implements
  eventual consistency across microservices.</p>
Accessible 
<p>The application uses a
  <dfn title="An architectural style for web services that uses standard HTTP methods">RESTful API</dfn>
  with <a href="/glossary#oauth-pkce">OAuth 2.0 PKCE flow</a>
  for authentication and implements
  <dfn title="A consistency model where all nodes will eventually reflect the same data, though not immediately">eventual consistency</dfn>
  across microservices.</p>

Idioms used without context or explanation

Content uses idiomatic expressions or figurative language that may not be understood by non-native speakers or people with cognitive disabilities.

Inaccessible 
<p>We need to move the needle on accessibility
  before the rubber meets the road with EAA
  enforcement.</p>
Accessible 
<p>We need to make measurable progress on
  accessibility before EAA enforcement begins
  and compliance becomes mandatory.</p>

Abbreviations and acronyms without expansion

Abbreviations and acronyms are used without being expanded on first use or linked to definitions, particularly problematic for screen reader users.

Inaccessible 
<p>Ensure your CMS meets WCAG AA by running
  VPAT assessments with AT.</p>
Accessible 
<p>Ensure your <abbr title="Content Management System">CMS</abbr>
  meets <abbr title="Web Content Accessibility Guidelines">WCAG</abbr>
  Level AA by running accessibility assessments with
  <abbr title="assistive technology">AT</abbr>
  such as screen readers.</p>

How to Test

  1. Read through content and identify all technical terms, jargon, idioms, and words used in specialized or unusual ways.
  2. Verify that each unusual term has a mechanism for providing its definition, such as a dfn element, abbr with title, inline explanation, or link to a glossary.
  3. Check that the glossary or definition mechanism is easy to find and use, and that users can return to their place in the content after reading a definition.
  4. Test with users who are not domain experts to identify terms that may need additional explanation.
  5. Verify that abbreviations and acronyms are expanded on first use on each page.

CMS-Specific Guidance

This criterion commonly causes issues on these platforms:

Further Reading

Related WCAG Criteria