Resource guide
3.1.3 Unusual Words
A mechanism must be available to identify definitions of unusual words, idioms, and jargon.
By Calling All Minds·Last updated April 2026
Success criterion
Conformance level
Enhanced accessibility — beyond the legal minimum.
What it means
Specialist vocabulary, idioms, and jargon can exclude users with cognitive disabilities, users reading in a second language, and anyone unfamiliar with a particular field. Providing definitions helps all of these users.
The mechanism for providing definitions can include: an inline glossary link, a tooltip, a definition list at the end of the page, or a linked glossary page.
In practice
Link technical terms to a glossary on first use in each section.
Use the HTML dfn element to mark up the defining instance of a term.
Use abbr with a title attribute to expand abbreviations and acronyms.
Plain language writing reduces the need for definitions in the first place.
Common failures
- Technical documentation with specialist terms and no glossary or definitions
- Legal text with complex terminology and no plain-language explanations
AXS Audit
AXS Audit checks your site against 3.1.3 and flags issues your team can act on straight away. It covers criteria that automated scanners often miss.