Depends on your definition of 'collective noun.' If you mean a plural noun, the most common way is to ad an S to the end. A true collective noun, however, is unique to each situation and you just...
brighter No, brighter is the comparative of bright. That is an adjective. Brightly is the adverb. If you want to make bright into a noun, use brightness. Adding ness to the end of a lot of adjectives...