A term that describes the special responsibility that a person has towards the creator of an instrument. Generally, a person with a fiduciary relationship to another has a duty to put the other person’s interests ahead of the person’s own. So, even if one person has transferred decision-making authority to a second person, the second person does not have complete discretion to exercise that authority. Instead, the second person must exercise that authority in a way that clearly benefits the first person. For example, an agent appointed by a power of attorney generally has a fiduciary duty to the principal.