Inside, he found a note from...

[sunsunmoon]

Inside, he found a note from Saki Arikawa, four origami flowers, and a photo of Saki's sixth grade class in Kagoshima.
(From Hawaii sailor finds message in a bottle from Japan - Yahoo! News)

Is the Inside an adverb?

[Rover_KE]

Yes.

[Route21]

Many thanks, Rover.

I was initially confused, as a NES but not an English teacher.

I read the sentence as being short for: "Inside the bottle...." and so didn't think of it (as I should have done) as an adverb.

In addition, I have traditionally thought of adverbs as words, predominantly ending in "-ly", that modify verbs, whereas in fact (as in adverb - definition of adverb by the Free Online Dictionary, Thesaurus and Encyclopedia.) they represent:

"a word or group of words that serves to modify a whole sentence, a verb, another adverb, or an adjective; for example, probably, easily, very, and happily respectively in the sentence They could probably easily envy the very happily married couple"

Inside is actually an interesting and versatile word, having looked it up: inside - definition of inside by the Free Online Dictionary, Thesaurus and Encyclopedia. - it can be used as a noun, adjective, adverb or preposition.

You live and learn every day!

Regards
R21