writing vs penning

writing and penning both are nouns.

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

As nouns, writing and penning are synonyms defined as:

Other synonyms of writing include authorship, composition.

writing (noun)	penning (noun)
the activity of putting something in written form	the act of creating written works
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