connective N1 uncommon casualwritten

〜じゃあるまいし — it's not as though ~ / since it isn't ~

〜じゃあるまいし・じゃあるまいし

Meaning

it's not as though / since it isn't ~ — casual twin of ではあるまいし; throws out an absurd premise, usually before a rebuke

子供こどもじゃあるまいし、泣なくのはやめなさい。

You're not a kid, so stop crying.

Attaches to	Form	Example
Noun or plain form	N／普通形 + じゃあるまいし

When: Conversational, often exasperated; sets up advice or criticism.

金持かねもちじゃあるまいし、そんな高たかい物ものは買かえないよ。

It's not as if I'm rich — I can't buy something that expensive.

嘘うそじゃあるまいし、そんなに疑うたがわないでくれ。

It's not like it's a lie, so don't be so suspicious.

Jengo shows 〜じゃあるまいし the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Sources Compiled with reference to A Dictionary of Advanced Japanese Grammar.