不知道…grammar point · tier 1 · 不知道… framing an embedded question (I don't know whether/who/when…)
Marks the speaker's own uncertainty about an embedded question, with no answer asked of the listener.
字源 FORM what the parts do
知 is an arrow (矢) beside a mouth (口), the answer that flies straight and fast; 道 is the road (辶) those words take out. 不 stops both, and the question sits downstream, unreached.
故事 STORY a scene to remember it by
An arrow nocked, a mouth open, the target lost in fog — nothing is loosed, and the question hangs in the air.
字源自撰記憶法
框 · Frame
不知道 [embedded question (能不能 / 是不是 / 誰 / 什麼時候 …)]
觸 · Trigger
You want to voice that something is unknown to you and hand the open question forward without demanding an answer.
序 · The move
1Open with 不知道 to flag your own uncertainty.Are you stating you don't know, not asking the listener?
2Drop the unsettled matter in as a question kept whole: A-not-A (能不能), 是不是, or a question word (誰 / 什麼時候).Is the embedded part still shaped like a question, not a flat statement?
3Leave it unanswered — no 嗎, no answer expected back.Would a listener feel obliged to reply? If so, you have built a real question, not 不知道.
例 · Examples
1不知道don't know明天早上六點tomorrow morning at six能不能able-not-able / whether (one) can起得來can get up。
I don't know whether I can get up at six tomorrow morning.
A-not-A alone (能不能起得來？) asks the listener to decide; tuck it under 不知道 and it becomes the thing you don't know, no longer a request for an answer.
不知道你來嗎？ → 不知道你來不來。 (an embedded question takes A-not-A or 是不是, not sentence-final 嗎)
不知道他是學生嗎？ → 不知道他是不是學生。 (whether-clause inside 不知道 uses 是不是, not 嗎)
我不知道。能不能起得來？ → 不知道能不能起得來。 (keep the question embedded under 不知道, not split off as a separate question)
English lets 'I don't know if…' keep the word 'if'; Chinese has no such conjunction here — the embedded yes-no question is carried by A-not-A (能不能) or 是不是, and 嗎 must not appear inside.