busy vs busyness

busy is not a noun while busyness is a noun.

Word	Noun	Adjective	Verb	Adverb
busy	No	Yes	Yes	No
busyness	Yes	No	No	No

busy (noun)	busyness (noun)
	the state of being or appearing to be actively engaged in an activity

busy (adjective)	busyness (adjective)
actively or fully engaged or occupied
overcrowded or cluttered with detail
intrusive in a meddling or offensive manner
(of facilities such as telephones or lavatories) unavailable for use by anyone else or indicating unavailability; (`engaged' is a British term for a busy telephone line)
crowded with or characterized by much activity

busy (verb)	busyness (verb)
keep busy with