In the following sentence, what does hopefully mean, what part of speech is it, and what does it modify?
Hopefully the rain will end soon.
From http://www.merriam-webster.com/dictionary/hopefully:
1 : in a hopeful manner
2 : it is hoped : I hope : we hope : hopefully the rain will end soon
It must be #2 according to the example. If it means "it is hoped" or "I hope" then is the entire main subject and predicate of the sentence subsumed into the word hopefully?
A related question is, if I use a comma, how does that change the sentence grammatically and semantically?
Hopefully, the rain will end soon.