毕竟／究竟／到底
毕竟: after all. 究竟, 到底: (what) on earth; in the end
Structure
毕竟 事实 ， … · 究竟／到底 疑问 ？
What it means
毕竟 states a fact that settles the matter: “after all”. 究竟 and 到底 press for the real answer: “(what) on earth”.
How it is built
毕竟 + fact: 他毕竟是长辈，你别跟他吵 (he is your elder, after all). 究竟／到底 + question: 你到底回不回家过年？ (are you coming home for New Year or not?)
When to use it
究竟 is more written, 到底 spoken; both come before the question word, the A不A form or 是…还是…. In statements 到底 can mean “finally” (他到底还是来了) or, like 毕竟, “after all”.
Watch out
毕竟 never appears in a question, and a 究竟／到底 question cannot end in 吗: ✗ 你到底去吗？ ✓ 你到底去不去？
Examples
家里这么多亲戚，你究竟是怎么记住的？
With so many relatives in the family, how on earth do you remember them all?
他毕竟是长辈，说话再不客气，你也别跟他吵。
He is your elder, after all: however rude he is, do not argue with him.
你到底回不回家过年？票快卖完了。
Are you coming home for New Year or not? The tickets are nearly gone.
Learn this in Lesson 38 · HSK 5–6: 亲戚怎么叫 (What to call your relatives)
A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.
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