writing vs activity

writing and activity both are nouns.

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

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

writing (noun)	activity (noun)
the activity of putting something in written form	any specific behavior
the act of creating written works	the trait of being active; moving or acting rapidly and energetically
the work of a writer; anything expressed in letters of the alphabet (especially when considered from the point of view of style and effect)	an organic process that takes place in the body
letters or symbols that are written or imprinted on a surface to represent the sounds or words of a language	a process existing in or produced by nature (rather than by the intent of human beings)
(usually plural) the collected work of an author	the state of being active
	(chemistry) the capacity of a substance to take part in a chemical reaction