I don't think there is a precise interpretation of italics. The idea of 'emphasis' is as close to their effect as II can get. If you were reading the sentence aloud, you would emphasize thatthat word. Just as we use spokenspoken emphasis to convey a variety of meanings, so do we use italics.
The meaning needs to come from the contextcontext, and the interpretation of the reader. Sorry!
ETA: Edited to add more italics!!!