なんです

auxiliary

it is that ...; the thing is ...

Polite explanatory/assertive auxiliary attached to nouns and na-adjectives. Adds a tone of explanation, emphasis, or seeking agreement. Equivalent to のです with politeness.

See also: のです

• これは私わたしの本ほんなんです。

  This is my book (you see).

• 彼かれは学がく生せいなんです。

  He is a student (that's the situation).