(1) In the contexts of international relations, peace and security, environmental matters and so forth, the term refers to the obligation of States to take preventive measures. E.g., the obligation of States regarding the problems of pollution, environmental protection and the law on non-navigational uses of international watercourses, or regarding the treatment of major equipment provided by a troop-contributing country to another.

(3) More generally, the reasonable standard of care for the environment and for the health and safety of others that individuals are expected to exercise in the course of their actions and duties.

(2) In a financial or investment context, a process undertaken by potential financiers or investors -- individuals or institutions -- to assess the value, risk and potential of an investment opportunity. From the Global Investor Glossary: "The process that companies, or more particularly their lawyers and accountants, carry out when one is about to acquire another. Basically, due diligence involves checking as much as possible about a company's financial performance and its liabilities before a deal is done, so that there are no nasty surprises afterwards. If, despite due diligence, there are some unforeseen surprises, the lawyers and accountants can expect heavy criticism from their client and possibly a lawsuit for negligence."