The word either can be an adjective. Another word to use is whichever.
It is an adverb.
spreading
When using an adjective to describe one thing, use the positive degree. (Wikipedia)
adverbs
Tattered is a verbal (past tense, past participle) that can be used as an adjective, much moreso than its use as a verb (to tatter).
Much can be an adjective or adverb, and more rarely a noun. There isn't much time. (adjective) These seeds are much smaller. (adverb) He didn't eat much. (noun)
Well, a lot is actually two words. The word "a" is an adjective and the word lot could be an adjective the way you use it. The words "a lot" are actually informal substations for the words many and much.
Happy is already an adjective.
Yes, you can use the adjective dramatic.
The adjective form for the verb to use is the past participle, used (a used car).The adjective form for the noun use is useful(useful information).
more, most
Yes, It Almost Has The Meaning As The Adjective.
Yes, the term 'untidy clothes' is a correct use of the adjective.
a good adjective is ugly
the adjective is captive - the noun is captivity
Yes you can use it as an adjective by saying someone is 'arachnophobic'