～んだもん JLPT N3 Casual
〜nda mon
Used to convey a sense of justification; 'because', 'that's why', 'it's just that'.
Very casual, whiny/pouty justification; strongly associated with children or exaggerated pouting for effect.
Formation
Verb-casual + んだもん, い-Adjective + んだもん, な-Adjective + なんだもん, Noun + なんだもん
Explanation
The ～んだもん grammar point is used when someone wants to give a reason, justification, or explanatory information in a more casual and emphatic way. It can be translated as 'because', 'that's why', or 'it's just that' in English. The formation differs depending on whether it is used with a verb, い-adjective, な-adjective, or noun.
Example sentences
遅れたんだもん、ごめん。
I was late, that's why I'm sorry.
Okureta nda mon, gomen.
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It's delicious, that's why I want to eat more.
Oishii nda mon, mou chotto tabetai.
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I'm tired, that's why I want to go to bed early.
Tsukarete iru nda mon, hayaku netai.
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He's my friend, that's why I can't not help him.
Kare wa tomodachi nan da mon, tetsudawanai wake ni wa ikanai.