I don't understand how all the nords thought dragons were only legend until they appeared. What? you telling me noone wondered what those big burial sites were for and didn't dig one up. Or am i missing something? where they speically sealed up or something? I mean come on they had a dragon graveyard right in there own back yard lol.
To further WTFlag's point
A legend (http://en.wikipedia.org/wiki/Latin, legenda, "things to be read") is a http://en.wikipedia.org/wiki/Narrative of human actions that are perceived both by teller and listeners to take place within human history and to possess certain qualities that give the tale http://en.wikipedia.org/wiki/Verisimilitude_(literature). Legend, for its active and passive participants includes no happenings that are outside the realm of "possibility", defined by a highly flexible set of parameters, which may include http://en.wikipedia.org/wiki/Miracle that are perceived as actually having happened, within the specific tradition of http://en.wikipedia.org/wiki/Indoctrinationwhere the legend arises, and within which it may be transformed over time, in order to keep it fresh and vital, and http://en.wikipedia.org/wiki/Realism_(arts).
I.e. It is entirely possible that dragons did exist (in fact it is proven). But they do not exist NOW.
History is interchangable with legend, in this context.