interlocutor; person one is talking with
Refers to the other party in a formal conversation, interview, or dialogue. Often used in contexts like panel discussions, interviews, or literary dialogues.
I answered the interlocutor's questions politely.
He appeared on the program as an interlocutor.
聞き手 emphasizes the listener role, often in an interview setting, whereas 対談者 can be either speaker or listener in a dialogue.
Compound of 対談 (taidan, 'dialogue') + 者 (sha, 'person'). The exact historical derivation is straightforward; the word follows a common pattern for forming agent nouns.