The word "as" is a conjunction in this sentence; in fact, the two together are being used as correlative conjunctions. See the first example under conj. below:
http://www.answers.com/as
In the sentence, "He is as sly as a fox", what part of speech is "as"? Is "as sly as a fox" an adjective? Is "sly" the object of a preposition? I am so confused. Thank you!
2 answers
The word "sly" is an adjective. The word "fox" is a noun. Taken all together, it's a simile.
http://www.google.com/search?q=idiom+%22as+sly+as+a+fox%22&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7SUNA
http://www.google.com/search?q=idiom+%22as+sly+as+a+fox%22&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7SUNA