Duplicity is dishonest behaviour that is meant to trick someone. The person (or the group) shows one face and hides another: they say one thing, and they mean, or do, something else. It is not only one small lie in the moment. It is a way of acting with a hidden side — two stories at once. Newspapers, courts, and rather formal writing like this word. Friends would more often say someone is two-faced, or that they lied. Though actually, duplicity feels bigger and colder than a single fib: it names the pattern, the double dealing. You can speak of a person's duplicity, or of duplicity in politics or in business. It is always a bad thing in ordinary use; nobody is proud of it.