duty

the social force that binds you to the courses of action demanded by that force; "we must instill a sense of duty in our children"; "every right implies a responsibility; every opportunity, an obligation; every possession, a duty"- John D.Rockefeller Jr

work that you are obliged to perform for moral or legal reasons; "the duties of the job"

a government tax on imports or exports; "they signed a treaty to lower duties on trade between their countries"