I know that I may be annoying right now, but I'd want someone to tell me. The correct word here would be χορτοφάγο. The adjective for vegetarian in the meaning of "doesn't eat meat (also as herbivorous)" is ο χορτοφάγος- η χορτοφάγος - το χορτοφάγο. The adjective for "appropriate for vegetarians" is ο χορτοφαγικός- η χορτοφαγική- το χορτοφαγικό. So a vegetarian diet is χορτοφαγική δίαιτα but an animal as a cow is χορτοφάγο.
I translated this sentence: the lion does not eat the hamster. Duolingo says it's wrong..... even though the give the translation for χαμστερ as hamster, hamsters. Both should be correct. Another correct solution, they say is HAMSTERS... which is the same way I translated it a second time.