Radix

Radix simpliciter pro rafano domestico accipitur, sic romani hodie, sic greci etiam vocant, nam riza gre. radix si sine adiuncto invenitur pro rafano domestico accipiunt interdum et rafanos vocant.

‘Radix’ {lit. “root”} on its own is used for ‘rafanus domesticus’ {“garden radish”}, and this is what the Romans say nowadays. The Greeks express it the same way, for ‘riza’ {lit. “root”} is the same in Greek as ‘radix’, and when it occurs without any epithet they use it for ‘rafanus domesticus’ {“garden radish”}, and sometimes they also call it ‘rafanos’.

Latin radix means “a root of a plant” and in particular “an edible root, esp. a radish”

ρίζα, /rhiza/, as Simon says, is the Greek word corresponding to Latin radix.

Greek ῤάφανος /rhaphanos/ “cabbage; radish” was adopted early on into Latin as raphanus, with the narrowed meaning “radish”