首先請看下列例句：
1. later they discovered, what was news to him, that pamela was the headmaster’s daughter.
2. she is bright, and what is better,amiable.
3. she wore,what was common at that time,a red shirt.
從以上例句可以看出，這裡的what似乎起了一種指代作用，這些句子完全可以改為下面的句子：
a. later they discovered that pamela was the headmaster's daughter, which was news to him.
b. she is bright and amiable, which is better. （與原句意義不符合）
c. she wore a red shirt, which was common at that time.
由以上的轉換我們基本上可以得出不完全的結論，即，what可以引導插入語，一般情況下，what可以轉換為一個由which引導的非限定性定語從句。再如下面的例句：
4. jackie made us all annoyed, what was worse, he ruined all our plan.
5. he never joined in the usual sports of the boys, and what is remarkable, never went out in a boat on the river.
6. he is an interesting speaker, and, what is more important, he knows his subject thoroughly.
由以上例句，我們還可以看出，what在引導此類插入語時，其謂語動詞常為連繫動詞。如：
7. i lost the chance, what seemed worse, nobody would employ me.
另外對於what一詞，補充如下詞組和短語，請大家以饗：
1. and what not 等等。如：i bought sugar, tea, eggs and what not.
2. give what for 斥責、懲罰。如：i'll give you what for if you don't stop that noise!
3. guess what 告訴你一個訊息。guess what! the boss is getting married.
4. i'll tell you what 我有一個主意。如：i'll tell you what--i'll be leaving for london soon.
5. know what is what 了解情況，在行。如：he's a clever fellow; he knows what's what.
6. know what one's about 有頭腦；會處理困境。如：it's a dangerous job, but i know what it's about.
7. or what 還是怎么的。如：shall we go or what?
8. so what 那又怎么樣。如：you see he'll fire me. so what?
9. what for 做什麼用。如：what are you running for? what's this switch for?
10. what have you 等等這類東西；應有盡有。如：the store sells big ones, small ones, medium ones, or what have you.
11. what if 要是...怎么辦。如：what if she finds out that you've lost her book?
12. what is what 基本情況。如：when it comes to cooking, jenny knows what's what?
13. what of... 怎么樣？如：so much for the westbrooks. what of shelley? shelley gave his...
14. what of it? 那又有什麼關係呢？如：--this is the fourth time she's rung you in a week.--well, what of it?
15. what the devil/hell... 他媽的...什麼/怎么（表示氣憤。如：what the devil shall we do now?）
16. what with 由於...種種原因（多指不快之事）。如：what with the noise and the dogs we could hardly sleep late on sunday.