verbs - How to differentiate ～られる conjugation between passive form and potential form?

For verbs of group 2, whose ～ます form is formed by dropping the ending ～る from the plain form, both the passive and potential forms have the same conjugation: ～られる. Example:

食べられる
1. to be eaten
2. can eat / edible

Other than looking at the context, how do I differentiate between the two meanings?

Answer

I don't think you can differentiate them without looking at the context.

• 
  

  ハンバーガー　が・を　食べられる　→　I can eat hamburgers

  
  


• 
  

  ハンバーガーを食べられてしまった！　→　Someone ate my hamburger!!

  
  

With the passive form, you'll usually see the doer/"culprit", indicated by ～に／～によって (there are some rules about which to use, but that's beyond the scope of this topic):

• 父にハンバーガーを食べられることが多い　→　My hamburgers are often eaten by my father ("My father often eats my hamburgers")


• 「モナ・リザ」はダ・ヴィンチによって描かれた　→　The "Mona Lisa" was painted by DaVinci.

Don't forget that there is a third conjugation of this form that is a type of keigo (somewhat between normal politeness and super politeness)

• 課長は明日会議に行かれる　→　The section chief is going to the meeting tomorrow.