vigil vs agrypnia

vigil and agrypnia both are nouns.

Word	Noun	Adjective	Verb	Adverb
vigil	Yes	No	No	No
agrypnia	Yes	No	No	No

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

vigil: the rite of staying awake for devotional purposes (especially on the eve of a religious festival)
agrypnia: a vigil before certain feasts (as e.g. Easter)

Other hyponyms of vigil include viewing, wake.

vigil (noun)	agrypnia (noun)
a purposeful surveillance to guard or observe	a vigil before certain feasts (as e.g. Easter)
the rite of staying awake for devotional purposes (especially on the eve of a religious festival)
a period of sleeplessness