不知……好
not know what (how) one should …; to be at a loss
Structure
不知（道） 疑问短语 （才）好
What it means
“Not know what (or how) one should …”: you are at a loss. 好 at the end means “would be best”.
How it is built
不知（道）+ question phrase (怎么办, 说什么, 点什么, 去哪儿) + （才）好: 朋友突然哭了，我真不知说什么好 (my friend suddenly burst into tears, and I didn't know what to say).
When to use it
不知如何是好 is the set written phrase; in speech say 不知道怎么办才好. The 好 adds the sense of being stuck for the right choice, not just lacking information.
Watch out
Don't drop 好 or the question word. ✗ 不知道怎么办才 ✓ 不知道怎么办才好. ✗ 我真不知好 ✓ 我真不知说什么好.
Examples
负责接待的官员夹在中间，一时不知如何是好。
The officials in charge of receiving them were caught in the middle and for a while did not know what to do.
朋友突然哭了起来，我真不知说什么好。
My friend suddenly burst into tears, and I really didn’t know what to say.
菜单上的菜太多了，我都不知道点什么才好。
There were so many dishes on the menu that I had no idea what to order.
Learn this in Lesson 99 · HSK 6–7: 康乾盛世 (The High Qing of Kangxi and Qianlong)
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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