Is じゃ here another way of saying では


なんじゃ, the じゃ here is this supposed to be a way of saying では? I know the
expression means what. But I don't get what the じは here does. The inly other I
have is that it is a way of saying だ




なんじゃ can be a form of なのでは, なのだ, and なんだ. The じゃ part by itself can be either
では or だ. You need to see the context (especially the type of the person who is
saying なんじゃ).

  1. なんじゃ = なのでは  
(ん is an [explanatory-の](https://japanese.stackexchange.com/q/5398/5010); じゃ
is a contracted version of では)

>     * 今日は月曜日なんじゃ? = 今日は月曜日なのでは?  
>  Isn't it Monday today?
>     * 学生なんじゃ免許は取れない。 = 学生なのでは免許は取れない。  
>  If he's a student, he cannot get a license.

  2. なんじゃ = なのだ  
(ん is an explanatory-の, じゃ is an [old man's
copula](https://japanese.stackexchange.com/q/34193/5010))

>     * わしは100歳なんじゃ。 = わしは100歳なのだ。  
>  I am 100 years old.

  3. なんじゃ = なんだ  
(なん is 何 meaning "what", じゃ is an old man's copula)

>     * これはなんじゃ？ = これはなんだ？  
>  What is this?

Note that 2 and 3 are only said by stereotypical old people (mainly in
fiction), while 1 is something that can be heard in an ordinary business
settings in real life.

