If there is an abbreviation in the content, you can know the original word or meaning of the abbreviation. It can be said that it is also related to 3.1.3. Incidentally, in HTML 4.01, there are tags abbr (abbreviation .eg XML, HTML), acronym (acronym .eg LAN, NATO), which are markups of abbreviations and meaning that meaning abbreviations expanded with the title attribute Yes, but somewhat accessible and supported situation is awkward, so be careful.
In HTML5, acronym is obsolete. Let's mark up with abbr in HTML5.
|Principle||Understandable||Information and the operation of user interface must be understandable.|
|Guideline||Readable||Make text content readable and understandable.|
|Mechanisms can be used to identify the original word or meaning of the abbreviation.|