viability vs practicality

viability and practicality both are nouns.

Word	Noun	Adjective	Verb	Adverb
viability	Yes	No	No	No
practicality	Yes	No	No	No

As nouns, practicality is a hypernym of viability; that is, practicality is a word with a broader meaning than viability:

viability: capable of being done in a practical and useful way
practicality: concerned with actual use rather than theoretical possibilities

viability (noun)	practicality (noun)
(of living things) capable of normal growth and development	concerned with actual use rather than theoretical possibilities
capable of being done in a practical and useful way