How do I know if られる means passive or 'can do'?

Question

彼は先生に褒められました makes sense as passive ('he was praised'), but I've also seen られる forms that just mean 'can'. Same ending, same conjugation — how do native speakers (or anyone) tell them apart in real time?

Accepted Answer

For る-verbs (ichidan) the form really is identical for passive and potential — 食べられる can be 'is eaten (by someone)' or 'can eat'. Context and the presence of an agent marked with に is the main clue: 彼に食べられた (there's a に-marked agent doing it to someone) reads as passive. If there's no agent and the sentence is just about ability, it's potential. う-verbs are less ambiguous since passive uses われる-type endings while potential uses a different える ending (書ける, 読める), so it's really the ichidan verbs where られる gets shared between the two meanings.

Answer

Right, and worth flagging the irregulars too since they're easy to forget — する takes される, and くる takes こられる, both formed the same way regardless of which meaning you're going for. So the passive/potential split for irregulars comes down to the same context clues 16 described above, not a different ending.