〜んだから n da kara
〜んだから（n da kara）means “since (it's a fact); precisely because; after all”. Gives a reason the speaker treats as obvious or known, and emphasizes it strongly to justify advice, a request, a conclusion, or an emotional reaction. Formation: 普通形 + んだから（Aな・N は 〜なんだから／のだから）
since (it's a fact); precisely because; after all
N2Formation
普通形 + んだから（Aな・N は 〜なんだから／のだから）
Explanation
Gives a reason the speaker treats as obvious or known, and emphasizes it strongly to justify advice, a request, a conclusion, or an emotional reaction. Stronger and more emphatic than plain から; 〜んだから is the spoken form, 〜のだから the written/formal one.
Examples
Note
Often carries a scolding, urging, or self-evident tone. With な-adjectives and nouns use 〜なんだから (静かなんだから / 学生なんだから). The intensified 〜んだから〜なさい/〜てください pattern is common in advice and reproach.
FAQ
〜んだから — what does it mean and how is it used?
since (it's a fact); precisely because; after all. Gives a reason the speaker treats as obvious or known, and emphasizes it strongly to justify advice, a request, a conclusion, or an emotional reaction. Stronger and more emphatic than plain から; 〜んだから is the spoken form, 〜のだから the written/formal one.
〜んだから — how do you form it?
普通形 + んだから（Aな・N は 〜なんだから／のだから）
〜んだから — any usage notes?
Often carries a scolding, urging, or self-evident tone. With な-adjectives and nouns use 〜なんだから (静かなんだから / 学生なんだから). The intensified 〜んだから〜なさい/〜てください pattern is common in advice and reproach.