The fundamental law of the state, containing the principles upon which the government is founded and regulating the divisions of the sovereign powers, directing to what persons each of these powers is to be confided and the manner it is to be exercised. E.g., the Constitution of the United States.
Constitution is also the name of the instrument containing the fundamental laws of the state.
The constitution of a contract is the making of the contract. E.g., the written constitution of a debt.