Language of Parts

Understanding WCAG2.0

The natural language of each part of the contents is clearly indicated to the program. Any words or phrases that are part of the proper noun, technical terms, phrases whose languages are unknown, and immediately before and after the text are excluded.

If the basics are written in English and some quoting texts from other languages, it's a good idea to mark up the quoted language.

Also, it is a good idea to add a lang attribute to the a element in the language switching common to the header of multilingual site.

Principle Understandable Information and the operation of user interface must be understandable.
Guideline Readable Make text content readable and understandable.
Criterion Language of Parts
(3.1.2 AA)
Interpretation by program can be made as to which language the natural language of each phrase or phrase is. However, exclude proper nouns, technical terms, phrases whose languages are unknown, and words or phrases that are part of the language of the immediately preceding and succeeding texts.

URL of Techniques for WCAG 2.0