disappointment vs letdown

disappointment and letdown both are nouns.

Word	Noun	Adjective	Verb	Adverb
disappointment	Yes	No	No	No
letdown	Yes	No	No	No

As nouns, disappointment and letdown are synonyms defined as:

disappointment and letdown: a feeling of dissatisfaction that results when your expectations are not realized

disappointment (noun)	letdown (noun)
an act (or failure to act) that disappoints someone	a feeling of dissatisfaction that results when your expectations are not realized
a feeling of dissatisfaction that results when your expectations are not realized