purchasing vs viaticus

purchasing and viaticus both are nouns.

Word	Noun	Adjective	Verb	Adverb
purchasing	Yes	No	No	No
viaticus	Yes	No	No	No

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

purchasing: the act of buying
viaticus: purchasing insurance policies for cash from terminally ill policy holders

Other hyponyms of purchasing include shopping, catalog buying, mail-order buying, viatication.

purchasing (noun)	viaticus (noun)
the act of buying	purchasing insurance policies for cash from terminally ill policy holders