"You eat beef."
Translation:Tu mangi il manzo.
Mangiare is a 1st "group" verb as it ends with "-are" ; in Imperative , concerning the first group verbs and some other verbs , we use the conjugation ending in "a" (as that with lui/lei) instead of the normal "mangi" Whereas if we use "Mangi" , it's not supposed to mean the imperative case but it should mean "You are eating" , as a description.. For instance : if you are eating fish and I'm watching you doing so , I would say "Mangi il pesce" : You're eating the fish ... but if I am demanding you to eat Fish , I would say "Mangia il pesce !" : You there, eat the fish ! Hope that has been clear enough :)