What does the verb after なくちゃ or なくては mean?


If なくちゃ is followed by another verb, is it read as " _you must do X **or
else** Y will happen_" or " _you must do X **and then** Y will happen_"?

**Example:**  
In this sentence (from よだかの星):  
おまえは、曇ってうすぐらい日か、夜でなくちゃ、出て来ない。

**Is it:** "As for you, it must be a dim cloudy day or night... or else you
won't come out."  
**Or:** "As for you, it must be a dim cloudy day or night so that you won't
come out."




You are thinking of `なくちゃ` as `must`, but it's really just a contraction of
`なくては`. `なくてはならない` and `なくてはいけない` are used to mean "must", and sometimes the
final verb is dropped and `なくちゃ` by itself is used as a very casual way to
imply that something must be done.

However, especially in cases where something comes after the `なくちゃ`, it can
just mean `なくては`. See Jisho's definition
[here](http://jisho.org/search/%E3%81%AA%E3%81%8F%E3%81%A1%E3%82%83), and also
a related question
[here](https://japanese.stackexchange.com/questions/25567/%E3%81%AA%E3%81%8F%E3%81%A1%E3%82%83-is-
the-short-informal-
of-%E3%81%AA%E3%81%8F%E3%81%A6%E3%81%AF%E3%81%84%E3%81%91%E3%81%BE%E3%81%9B%E3%82%93-but-
why-is-
there-%E3%81%AA%E3%81%8F%E3%81%A1%E3%82%83%E3%81%84%E3%81%91%E3%81%AA%E3%81%84%E3%81%AE-
rather-than-%E3%81%AA).

In short, it's

> As for you, it must be a dim cloudy day or night or else you won't come out.

Edit: Also see Eiríkr Útlendi's comment.




You are thinking of `なくちゃ` as `must`, but it's really just a contraction of
`なくては`. `なくてはならない` and `なくてはいけない` are used to mean "must", and sometimes the
final verb is dropped and `なくちゃ` by itself is used as a very casual way to
imply that something must be done.

However, especially in cases where something comes after the `なくちゃ`, it can
just mean `なくては`. See Jisho's definition
[here](http://jisho.org/search/%E3%81%AA%E3%81%8F%E3%81%A1%E3%82%83), and also
a related question
[here](https://japanese.stackexchange.com/questions/25567/%E3%81%AA%E3%81%8F%E3%81%A1%E3%82%83-is-
the-short-informal-
of-%E3%81%AA%E3%81%8F%E3%81%A6%E3%81%AF%E3%81%84%E3%81%91%E3%81%BE%E3%81%9B%E3%82%93-but-
why-is-
there-%E3%81%AA%E3%81%8F%E3%81%A1%E3%82%83%E3%81%84%E3%81%91%E3%81%AA%E3%81%84%E3%81%AE-
rather-than-%E3%81%AA).

In short, it's

> As for you, it must be a dim cloudy day or night or else you won't come out.

Edit: Also see Eiríkr Útlendi's comment.

