3.1.3 Unusual Words

WCAG 2.2 · 3.1.3 AAA Understandable

What it requires

A mechanism must be available to identify the specific definition of words or phrases used in an unusual or restricted way — including idioms (whose meaning can't be deduced from the individual words, such as "spitting feathers") and jargon (terms used in a particular way by a specific field or community). This applies wherever such words appear in content. The "mechanism" can be a definition right there in the surrounding text, a link to a definition or glossary, an inline expandable definition, or a definition available through the page's structure.

  • People with reading and language disabilities (e.g. dyslexia) who cannot easily decode unfamiliar or specialized vocabulary.
  • People with cognitive disabilities who may not infer meaning from context or recognize idioms.
  • People who are Deaf and use sign language as a first language, for whom written idioms and jargon can be a barrier.
  • Anyone new to the subject domain encountering field-specific jargon.

How to detect it

Checks for identifying definitions of unusual words
Check How Catches it?
Find unusual words Manually read content; flag idioms, jargon, and words used in a restricted sense. Manual only — requires human judgement.
Definition available For each flagged term, confirm a definition is reachable (inline text, link, glossary, or <dfn>/definition list). Manual review.
Keyboard / screen reader If the mechanism is a link or expandable control, verify it is operable by keyboard and announced by a screen reader. Manual + AT.
Automated tools axe and similar scanners cannot identify which words are "unusual" or whether a definition exists. No — not automatable.

How to fix it

  1. Identify words and phrases used in an unusual or restricted way, plus idioms and jargon.
  2. Provide a definition for each — inline in the text, via a link to a glossary entry, or with an expandable inline definition.
  3. For first or key uses, mark the term with <dfn> and link to its definition so the relationship is programmatic.
  4. Maintain a consistent glossary so the same term resolves the same way throughout the site.
<p>
  The team was
  <dfn><a href="glossary.html#spitting-feathers">spitting feathers</a></dfn>
  waiting for the build to finish.
</p>

Copy-paste tests

Automated coverage

There is no fully automated axe-core rule for 3.1.3 Unusual Words — a tool cannot judge whether a word is idiomatic, jargon, or otherwise unusual. This criterion needs manual review using the console check and steps below.

Run this in the browser console

find-unusual-words.js 
// Surface definitions/abbreviations so you can review unusual words.
const marked = [...document.querySelectorAll('dfn, abbr[title], [aria-describedby]')];
console.table(marked.map(el => ({
  tag: el.tagName.toLowerCase(),
  text: el.textContent.trim().slice(0, 60),
  title: el.getAttribute('title') || ''
})));
marked.forEach(el => el.style.outline = '2px solid magenta');
console.log('Marked-up terms:', marked.length);

What to check manually: read the body text for jargon, idioms, or domain terms a general reader may not know, and confirm each truly unusual word has a definition mechanism (inline <dfn>, glossary link, or abbreviation expansion). The script can only flag existing markup, not missing definitions.