Fiduciary is an adjective that means ‘involving trust.’

The Latin word fidere (fie DARE ay) means ‘to trust.’ In the late 16th century, our word of the day joined the English language. Often used to describe the relationship between a trustee and a beneficiary of a firm, fiduciary may be used in more ordinary day-to-day contexts. Here’s an example:

After promising to watch her cats, I felt I had a fiduciary duty to miss the concert I’d been waiting weeks to see. Maintaining trust can often mean making sacrifices.