What are the supported languages for the attribute "lang" ?

Question

please, specify particular key word

Answer 1

Can't type all of them here, so look at this.

https://www.w3schools.com/tags/ref_language_codes.asp

Answer 2

If you go to the link I sent you...................

ISO Language Codes
The HTML lang attribute can be used to declare the language of a Web page or a portion of a Web page. This is meant to assist search engines and browsers.

Answer 3

"Note that you can have multiple languages on a single page"
how do we declare multiple lang ?

Answer 4

can anyone explain why is it used?