particle N3 common casual

もん — colloquial もの: a reason or excuse with a touch of defiance

もん

Builds on もの

Meaning

(it's) because ~ / but ~ — gives a reason or excuse, often pouty, childish, or defensive

Key sentence

だって、知しらなかったんだもん。

But it's because I didn't know!

Formation

Attaches to	Form	Example
Clause (plain form), sentence-finally	… + もん (casual contraction of もの)	行いきたくないもん / 疲つかれたんだもん

When: Very casual, common in children's, women's, and intimate speech. It often closes a sentence that begins with だって ('but'), defending oneself against a complaint or question.

Examples

食たべないの？ — だって、お腹なかいっぱいだもん。

You're not going to eat? — But I'm full!

まだ子供こどもなんだもん、しかたないよ。

He's still a kid, after all — it can't be helped.

When you can't use it

もん is sentence-final and emotionally coloured — it justifies oneself, so it doesn't fit neutral explanation in formal or written contexts. There, use から or ので.

Easily confused with

からから states a reason neutrally and works at any politeness level. もん gives the reason as a self-justifying excuse with a pouty or defiant feel, and is strictly casual. だってだって opens the excuse ('but…') at the front of the sentence; もん closes it at the end. They frequently pair up: だって〜もん.

Notes

もん is just the casual contraction of sentence-final もの. The full もの is slightly softer/more feminine; もん is more clipped and conversational.

See もん in real sentences

Jengo shows もん the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Study it in Jengo

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

← Back to the grammar tree