Comic and Gaphic Novel don't mean the same, or else they wouldn't be separate terms. It's rather like how cakes and biscuits are different.
Without looking up the actual definitions (if set definitions exist at all), I would say that a comic is shorter and has less text than a graphic novel, though a comic may be collected together and put in the form of a graphic novel (like Bone is). The structure of comics, I would say, is lighter, and less unified. A graphic novel has one main plot which is its chief focus -- a comic may have an overarching plot linking the segments together, but is not as focused on a main plot as a graphic novel is. Graphic novels are also more likely to have one of more narrators (e.g. boxes aside from speech bubbles that say more than merely 'meanwhile...')
-- this is just me thinking aloud, though. I'm not an expert on either form, though I still believe that there is a difference between them.
Tintin seems to have the structure of a graphic novel (one unified story), but the form of a comic (less text and no meta-text, e.g. narrator).
Please don't pick apart what I've just typed as if I think I'm an expert because these are really just thoughts!