A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon. (Level AAA)
This is about making your content accessible to people who may not understand certain words or words presented in certain ways.
There may be times when you need to present content for a specific audience that requires specialised terminology. What Success Criterion 3.1.3 requires is that you provide some way for people who do not already know to find out what a term means.
There may be times when you need to deliver content that relies on figurative terms, or nonliteral usage, or highly technical words, or words in unusual contexts. To achieve Level AAA compliance you will need to provide a way for the full meaning to be made available.
Conformance will benefit people with cognitive, learning and intellectual disabilities, as well as all people who have difficulty with anything other than plain language.
There is also a benefit to people who use screen readers, in that magnification tends to limit the visible context and thus the opportunity to work out meaning from surrounding words. Compliant content will cope better with magnification.
This might all seem difficult to implement but it becomes approachable once you understand the specific meaning of four concepts used in Success Criterion 3.1.3:
- unusual or restricted
- idioms and jargon
Once you have those clear, conformance becomes not only possible but a way of making your web content more effective.