Simplify the following text for a Grade 10 native English-speaking person.
Original: The word `` hippopotamus '' is derived from the ancient Greek , hippopotamos , from , hippos , `` horse '' , and , potamos , `` river '' , meaning `` horse of the river '' .
Simplified: The word `` hippopotamus '' comes from the ancient Greek , hippopotamos , from , hippos , `` horse '' , and , potamos , which means `` river '' .