disappointment
UK: ˌdɪsəˈpɔɪntmənt | US: ˌdɪsəˈpɔɪntmənt
n. the feeling of sadness or dissatisfaction when something hoped for does not happen
n. a person, event, or thing that causes such a feeling
The word "disappointment" originates from the Old French desapointer (to remove from office, undo an arrangement), combining dis- (expressing reversal) and apointer (to appoint or arrange). Over time, the meaning shifted from literal removal of an appointment to the emotional sense of unmet expectations. The suffix -ment nominalizes the action, solidifying its modern usage.
Her failure to win the competition was a great disappointment.
He hid his disappointment behind a smile.
The movie’s ending left the audience in disappointment.
Despite his efforts, the results were a disappointment.
She tried not to show her disappointment when the trip was canceled.