How many letters does the top answer for “what does hippopotamus mean and in what langauge” have?

The most common answer is greek (5 letters).

Crossword clue: what does hippopotamus mean and in what langauge

3 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

greek 5 letters otdb

of or relating to or characteristic of Greece or the Greeks or the Greek language

horse 5 letters otdb

solid-hoofed herbivorous quadruped domesticated since prehistoric times

river 5 letters otdb

a large natural stream of water (larger than a creek)