duty [duties](that which one is morally or legally obligated to do) noun [UK: ˈdjuː.ti] [US: ˈduː.ti]It's my duty to help you. = Es mi obligación ayudarte.
obligation [obligations](act of binding oneself by a social, legal, or moral tie to someone) noun [UK: ˌɒ.blɪ.ˈɡeɪʃ.n̩] [US: ˌɑː.blə.ˈɡeɪʃ.n̩]It is our obligation to help. = Es nuestra obligación ayudar.