The word fly (and the plural flies) is the noun form, a common concrete noun, a word for an insect.
The abstract noun form for the verb to fly is flyability.
The word fly is not an adjective; terms such as flypaper or fly-by are compound words. The adjective forms are the present participle, flying, and the past participle flown.
And, last but not least, the word 'fly' used as an adjective is a slang term.
The abstract noun form of the adjective unique is uniqueness.
The abstract noun form for the adjective truthful is truthfulness.The word 'truthful' is the adjective form of the abstract noun truth.
The adjective for the abstract noun "famous" is "famous."
The abstract noun for the adjective quick is quickness.
The abstract noun for the adjective hot is hotness.
The abstract noun for the adjective "humble" is humility. Humility refers to the quality or state of being humble, modest, or respectful.
The abstract noun form of the adjective triumphant is triumph.
The word 'delightful' is the adjective form of the abstract noun delight.The abstract noun form of the adjective 'delightful' is delightfulnerss.
The abstract noun form of the adjective 'useful' is usefulness.The word 'useful' is the adjective form of the abstract noun use.
The abstract noun for the adjective famous is famousness.The word 'famous' is the adjective form of the abstract noun fame.
The abstract noun form of the adjective 'opinionated' is opinionatedness.The word 'opinionated' is the adjective form of the abstract noun opinion.
Weak is an adjective, and the related abstract noun is weakness. Weariness is an abstract noun (the adjective is weary).