prospect vs expectancy

prospect and expectancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
prospect	Yes	No	Yes	No
expectancy	Yes	No	No	No

As nouns, expectancy is a hyponym of prospect; that is, expectancy is a word with a more specific, narrower meaning than prospect:

Other hyponyms of prospect include hope, promise, foretaste, possibility, anticipation, apprehension, misgiving.

prospect (noun)	expectancy (noun)
a prediction of the course of a disease	something expected (as on the basis of a norm)
the visual percept of a region	an expectation
belief about (or mental picture of) the future
someone who is considered for something (for an office or prize or honor etc.)
the possibility of future success

prospect (verb)	expectancy (verb)
explore for useful or valuable things or substances, such as minerals
search for something desirable