What does ○○ていない + といけない mean?


I've recently encountered a simple sentence in a
[video](https://www.youtube.com/watch?v=SEBLibNzayQ) that confused me
grammatically. (see 2:08)

> 子供が考える時には、 **待っていないといけない** ですよね。

My assumptions:

待っていない = negative continuous form of 待つ

といけない = have to

I've rarely seen this combination used in context and I can't find any
resources online that explain this usage.

My questions are:

  1. Why doesn't the speaker say 待たないといけない instead? As far as I understand, it would mean the same thing.
  2. In what situations would I use this combination ていない＋といけない?
  3. Am I correct in assuming this と is not the conditional と? If so, does this also apply to the other forms? i.e. ○○ていなくちゃいけない、ていなきゃいけない、ていないとだめ etc.

I appreciate any comments and feedback!




といけない does not mean "have to" by itself. と is "then", and いけない is "no good",
so the combined meaning of といけない is something like "then (it's going to be)
bad".

  * この本を子供が読むといけない。  
If kids read this book, then it's going to be bad.  
→ Kids shouldn't read this book.

You need to add another ない for it to mean "have to" (i.e., double negative):

  * 子供はこの本を読まないといけない。  
If kids don't read this book, it's going to be bad.  
→ Kids have to read this book.

Likewise:

  * 待つといけない。  
If you wait, then it's not good.  
→ You should not wait.  
→ Let's not wait.

  * 待っているといけない。  
If you keep waiting then it's not good.  
→ You should not keep waiting.  
→ Let's stop waiting.

  * 待たないといけない。  
If you don't wait, then it's not good.  
→ You have to wait.

  * 待っていないといけない。  
If you don't keep waiting, then it's not good.  
→ You have to keep waiting.

* * *

To answer your questions:

  1. 待たないといけない is also perfectly fine in this context, but the -teiru form implies you'll need to wait patiently for a while.
  2. Whenever you want the meaning of "keep ～ing", as you can see in the examples above.
  3. This と _is_ the conditional と [described here](https://japanese.stackexchange.com/a/1784/5010).




といけない does not mean "have to" by itself. と is "then", and いけない is "no good",
so the combined meaning of といけない is something like "then (it's going to be)
bad".

  * この本を子供が読むといけない。  
If kids read this book, then it's going to be bad.  
→ Kids shouldn't read this book.

You need to add another ない for it to mean "have to" (i.e., double negative):

  * 子供はこの本を読まないといけない。  
If kids don't read this book, it's going to be bad.  
→ Kids have to read this book.

Likewise:

  * 待つといけない。  
If you wait, then it's not good.  
→ You should not wait.  
→ Let's not wait.

  * 待っているといけない。  
If you keep waiting then it's not good.  
→ You should not keep waiting.  
→ Let's stop waiting.

  * 待たないといけない。  
If you don't wait, then it's not good.  
→ You have to wait.

  * 待っていないといけない。  
If you don't keep waiting, then it's not good.  
→ You have to keep waiting.

* * *

To answer your questions:

  1. 待たないといけない is also perfectly fine in this context, but the -teiru form implies you'll need to wait patiently for a while.
  2. Whenever you want the meaning of "keep ～ing", as you can see in the examples above.
  3. This と _is_ the conditional と [described here](https://japanese.stackexchange.com/a/1784/5010).

