The word Dragon was traslated in 1611 from the greek word Drakon (not to be confused with Draco which is the name given a constalation of star that resemble the shape of a Drakon or Dragon) Drakon is the greek translation of the Hebrew word Tanniynim which has a broad meaning.
In hebrew literature tanniynim is used as names or synonyms of the following or as a group name for a type(kind) of creature
1. Whale or great fish
2. Sea monster/Sea serpent
3. Leviathan (Livy^ath^an)
4. large reptile
5. Behemoth (Behemot, B`hemot, Bahimuth, Bahamut)
6. large flying serpents/reptiles
7. that old serpent aka the devil, satan
the first six entries above discribe creatures, who's existance has been proven by the fossil record of the earth but which fall under a different name, one which has yet to be associated with the word Dragon, for what ever reason. That name is Dinosaur
i.e. the Dragons of legend are Dinosaurs.
Dragons where assumed to be a mythological creature, however through studies of the myth compared with actual historical evidence, the myth of dragons can be best explained by giving them the name Dinosaur.