to adopt, approve and sanction an agreement or treaty by passing it into law
Under EU rules, the treaty cannot enter into force if any of the member states fails to ratify it.
to adopt, approve or sanction something that has already been agreed or signed
It was necessary for the shareholders to ratify board decisions regarding investments over 1,000,000 euros.
to settle, confirm or affirm by express or implied consent to something done or agreed to by an agent or servant
He accepted that his agent had acted in good faith and ratified the contract.