WCAG Guideline 3.1.3: Unusual Words Explained

Estimated read time: 5–6 minutes

Guideline 3: Understandable

The Understandable principle ensures that web content is clear and predictable, including the language and terms used.

Guideline 3.1: Readable

Guideline 3.1 focuses on making text content readable and understandable by identifying language and clarifying complex terms.

What Is Guideline 3.1.3 Unusual Words?

"A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon."

Guideline 3.1.3 requires that users can access definitions for words or phrases that are used in an unusual, technical, or restricted way.

Helps users understand jargon, idioms, and ambiguous terms
Essential for users with cognitive or learning disabilities
Applies to all web content with specialized or uncommon language

For more, see AccessGuide: Unusual Words .

Why Does It Matter?

Inclusivity: Explaining unusual words helps users with cognitive disabilities and non-native speakers.
Legal Compliance: Unusual Words is a Level AAA requirement in WCAG 2.1 and 2.2.
Usability: Improves comprehension for all users.

For more, see W3C’s guidance on Unusual Words .

What Needs Unusual Words Explained?

Jargon and idioms
Technical terms
Any word used in an unusual or restricted way

How to Make Unusual Words Accessible

Provide definitions for unusual words
Use tooltips, glossaries, or inline explanations
Document terminology conventions
Test with users who may not know the terms

For more, see the W3C's Unusual Words Techniques .

Common Mistakes to Avoid

Not explaining jargon or idioms
No glossary or definitions provided
Not documenting terminology conventions
Not testing with users who may not know the terms

Differences Between A, AA, and AAA for Guideline 3.1.3 in WCAG 2.2

Level A: Not applicable for this guideline.
Level AA: Not applicable for this guideline.
Level AAA: Requires a mechanism for identifying definitions of unusual words. This is the core requirement for 3.1.3 and is mandatory for AAA conformance.

For more, see the W3C’s official documentation for 3.1.3 Unusual Words .

Quick Checklist

Definitions are provided for unusual words
Tooltips, glossaries, or inline explanations are used
Terminology conventions are documented
Tested with users who may not know the terms

Guideline 3.1.3 is essential for helping users understand your site. By explaining unusual words, you support users with disabilities, improve usability, and meet legal requirements. Test your site regularly and make terminology accessibility a core part of your development process.

Accessibility means clarity—help users understand every word!

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