である
Usage
N / なA ~~な~~ + である means the same as -だ but is more formal. It is often used in writing.
Examples
失敗は成功の母である.
Failure is the stepping-stone to success
ここは去年まで山であった.
This area was a mountainous forest until last year.
Good to know
のです ✍️ becomes in that style のである。