I remember seeing a talk by Scott Hahn where he said the Hebrew word that has been translated to serpent in Genesis is the same word that was translated to dragon in Revelation. That actually makes a lot more sense.
I’ve done some checking and it emerges that the true answer is a bit different from that.
In the OT, the Hebrew word for the serpent in Genesis is
nachash. In English Bibles, this word, as far as I can tell, is invariably translated as either “serpent” or “snake”, never “dragon” or anything else.
In the Septuagint,
nachash is always translated as
ophis, which is the usual Greek word for snake.
In the NT, when Paul quotes the story of Eve and the serpent in 2 Cor 11:3, the Greek word he uses is the same one,
ophis.
Finally, in Revelation, we find the dragon and the serpent mentioned in the same verse: ,
And he seized the dragon, that ancient serpent, who is the devil and Satan, and bound him for a thousand years. (Rev 20:2)
The Greek words used in this verse are
drakon for dragon and
ophis for serpent.