〜もの／〜もん

だって、忙(いそが)しかったんだもん。

Datte, isogashikatta n da mon.

But I was busy, you know.

もの and もん make an excuse, often arriving with だって

まだ子供(こども)なんだもの。

Mada kodomo na n da mono.

They are still a child, after all.

It is intimate, and stays out of formal or upward talk

知(し)らなかったんだもん、しょうがない。

Shiranakatta n da mon, shōganai.

I did not know, so what could I do.

It often closes with しょうがない, sliding out from under the blame