exigency vs necessity

exigency and necessity both are nouns.

Word	Noun	Adjective	Verb	Adverb
exigency	Yes	No	No	No
necessity	Yes	No	No	No

As nouns, necessity is a hypernym of exigency; that is, necessity is a word with a broader meaning than exigency:

exigency: that which is required in a particular situation —usually used in plural.
necessity: the condition of being essential or indispensable

exigency (noun)	necessity (noun)
a sudden unforeseen crisis (usually involving danger) that requires immediate action	anything indispensable
a pressing or urgent situation	the condition of being essential or indispensable
that which is required in a particular situation —usually used in plural.