んです・
んです and のです present a statement as the explanation or relevant background for a situation. In a question, they ask the listener to explain what is behind something noticed or already under discussion.
Connecting a fact to the situation
This pattern does more than state a fact. It presents that fact as helping to explain something the speaker and listener can see, know, or are already discussing. Depending on context, English may use “the thing is,” “it is because,” or simply a natural statement of the reason.
Asking for and giving an explanation
The question asks what explains the open window. The answer presents the room's temperature as that explanation.
With a noun
明日は休みなんです。だから、今夜は少し遅くまで起きています。
I have tomorrow off, so I am staying up a little later tonight.
AnalyzeBecause 休み is a noun, the present affirmative form is 休みなんです.
Conversation and writing
んです is extremely common in polite conversation. The uncontracted のです sounds more deliberate, formal, or written. In plain-style conversation, the corresponding forms are んだ and のだ; choose the ending that matches the politeness of the surrounding conversation.
More examples
電車が遅れたんです。それで、会議に間に合いませんでした。
The train was delayed. That is why I did not make it to the meeting on time.
Analyzeそのかばん、どこで買ったんですか。
Where did you buy that bag?
Analyzeこの部屋は少し寒いんです。窓を閉めてもいいですか。
This room is a little cold. May I close the window?
Analyzeすみません、肉は食べないんです。
Sorry, I do not eat meat.
Analyze昨日は祝日だったんです。それで、銀行が閉まっていました。
Yesterday was a public holiday. That is why the bank was closed.
Analyzeこの店は静かなんです。ここでゆっくり話しましょう。
This place is quiet, so let us talk here without rushing.
Analyzeこの地域では、月曜日に休館する図書館が多いのです。そのため、利用する前に予定を確認してください。
In this area, many libraries are closed on Mondays. That is why you should check their schedules before visiting.
Analyze