noun
written pledge; memorandum; signed assurance
A formal written document in which one party promises or confirms something, often used in legal, business, or official contexts. Can range from a simple signed note to a more formal instrument.
契約の前に、念書を交わしておきましょう。
Let's exchange a written pledge before the contract.
彼は借金の念書を書かされた。
He was made to write a memorandum of the debt.