writing vs lexicography

writing and lexicography both are nouns.

Word	Noun	Adjective	Verb	Adverb
writing	Yes	No	No	No
lexicography	Yes	No	No	No

As nouns, lexicography is a hyponym of writing; that is, lexicography is a word with a more specific, narrower meaning than writing:

writing (noun)	lexicography (noun)
the activity of putting something in written form	the act of writing dictionaries
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