The word "dinosaur" is derived from the Ancient Greek words "deinos" and "sauros," which together mean "terrible lizard." The term was first used to describe dinosaurs by British paleontologist Richard Owen in 1842.
The word "dinosaur" does not exist in Ancient Greek because the concept of dinosaurs did not exist in ancient times. The term "dinosaur" was coined in 1841 by Sir Richard Owen to describe the prehistoric reptiles whose fossils were being discovered at the time.