〜もの
Formation
Meaning
An informal expression used to give a reason or excuse. Often used by children or in causal speech to sound a bit emotional or to seek sympathy.
Note
A sentence-ending particle used to provide an explanation or excuse in a soft, often emotional way. It is particularly common in the speech of children and young people, often conveying a sense of petulance, seeking sympathy, or as a way to soften a justification. The variant 'もん' is very common in casual speech and often follows '〜んだ'.
Examples
どうして食べないの？ ーだって、美味しくないんだもん。
Why aren't you eating? -Because it's not delicious, you see.
あんなところ、もう二度と行かないもの。
I'll never go to a place like that again (because...).
どうして遅れたの？ ー道が混んでいたんだもん。
Why were you late? -Because the road was crowded, you see.
そんなこと言ったって、仕方のないことだもの。
Even if you say that, it can't be helped (because...).
テスト勉強しなくていいの？ ーだって、もう全部覚えたんだもん。
Is it okay not to study for the test? -Because I've already memorized everything, you see.
もう寝るの？ ーだってお腹が空いたんだもん。
Are you going to bed already? -Because I'm hungry, you see.
そんなに怒らないで. ーだって、彼が意地悪をするんだもん。
Don't be so angry. -Because he's being mean, you see.
一人で行けるの？ ーうん、もう子供じゃないもん。
Can you go by yourself? -Yeah, I'm not a child anymore, you see.