Dragons are might monsters known to fly, summon fire from their mouths, horde treasure, fight knights and kidnap princesses. In other mythologies Dragons are masters of Water, Weather, and symbols of Imperial Power.
Now what are dinosaurs, big, sometimes enormous creatures of an age long passed. While past imagining of dinosaurs have them appearing as reptiles, modern day paleontologist theorize that many dinosaurs would've had feathers and are more closely related to birds than reptiles.
Dragons: A brief history of the mythical, fire-breathing beasts
Wikipedia: Chinese Dragons. . .
National Museum of Natural History (a New View of the T. Rex)
Hollow Bones and perfect Respiratory Systems. . .
Dinosaurs' Unique Bone Structure. . .
https://www.unearthingtrex.com/pages/rex_traits.html
Paleontologist's New Theory for Short Arms: Feeding Evolution
T Rex's Speed (livescience)
T Rex's Speed (Smithsonian)