What single noun denotes a person who is interested in something?
Solution 1:
enthusiast (ODO)
noun
1 A person who is very interested in a particular activity or subject:
a sports car enthusiast
syn: fan, … supporter, follower; … informal buff, …
Cited on TFD:
He was as much of an enthusiast in art as I was, and not less anxious to learn to paint. A Tramp Abroad by Twain, Mark