Sentence-Ending の
〜の (question/explanation)
の at the end of a sentence adds an explanatory tone or asks for explanation — equivalent to 'it is that...' or 'is it that...?'
Pattern
Verb/Adjective + の (casual) / んです (polite)
Explanation
When の (or its polite form んです/のです) appears at the end of a sentence, it adds an explanatory nuance. It's like saying 'the thing is...' or 'it's that...'
'どうしたんですか' (What happened? — asking for explanation) vs 'どうしましたか' (What did you do? — simple question). The んです version seeks the story behind something.
In casual speech, の alone serves this function: '何を食べるの？' (What are you going to eat?). This is very common in daily conversation and is softer than a plain question.
Examples
どこに行くんですか。
どこにいくんですか。
Doko ni iku n desu ka.
Where are you going? (seeking explanation)
頭が痛いんです。
あたまがいたいんです。
Atama ga itai n desu.
The thing is, I have a headache.
明日テストがあるんです。
あしたてすとがあるんです。
Ashita tesuto ga aru n desu.
The thing is, I have a test tomorrow.
何を食べるの。
なにをたべるの。
Nani wo taberu no.
What are you going to eat? (casual)
Common Mistakes
Wrong
頭が痛いです。
Correct
頭が痛いんです。
Without んです, it is a plain statement. With んです, it implies you are explaining why you can't do something.
Wrong
きれいだんです。
Correct
きれいなんです。
After な-adjectives, use な + んです, not だ + んです.
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