writing vs written language

writing and written language both are nouns.

Word	Noun	Adjective	Verb	Adverb
writing	Yes	No	No	No
written language	Yes	No	No	No

As nouns, written language is a hypernym of writing; that is, written language is a word with a broader meaning than writing:

writing: the work of a writer; anything expressed in letters of the alphabet (especially when considered from the point of view of style and effect)
written language: communication by means of written symbols (either printed or handwritten)

Other hypernyms of writing include black and white, written communication.

As nouns, written language is a hypernym of writing; that is, written language is a word with a broader meaning than writing:

writing: letters or symbols that are written or imprinted on a surface to represent the sounds or words of a language
written language: communication by means of written symbols (either printed or handwritten)

Other hypernyms of writing include black and white, written communication.

As nouns, written language is a hypernym of writing; that is, written language is a word with a broader meaning than writing:

writing: (usually plural) the collected work of an author
written language: communication by means of written symbols (either printed or handwritten)

Other hypernyms of writing include body of work, oeuvre, work, black and white, written communication.

writing (noun)	written language (noun)
the activity of putting something in written form	communication by means of written symbols (either printed or handwritten)
the act of creating written works
the work of a writer; anything expressed in letters of the alphabet (especially when considered from the point of view of style and effect)
letters or symbols that are written or imprinted on a surface to represent the sounds or words of a language
(usually plural) the collected work of an author