Which one (of several)? — a word used to ask which item among several options.
この中でどれか分かりますか？
Do you know which one this is among these?
どれか一つ選んでください。
Please choose one of them.
彼は『どれか？』とだけ答えた。
He answered only, 'Which one?'
One of; any one of — refers to one item among several (often used in constructions like 'どれか〜').
このボタンのどれかを押してください。
Please press one of these buttons.
参加者のどれかが代表として話す予定です。
One of the participants is scheduled to speak as a representative.
記憶している言葉はどれかありますか？
Is there any word you remember?