youth vs puppy

youth and puppy both are nouns.

Word	Noun	Adjective	Verb	Adverb
youth	Yes	No	No	No
puppy	Yes	No	No	No

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

Other hyponyms of youth include blade, hobbledehoy, pup, pupil, school-age child, schoolchild, slip.

youth (noun)	puppy (noun)
the freshness and vitality characteristic of a young person	a young dog
young people collectively	an inexperienced young person
a young person (especially a young man or boy)
early maturity; the state of being young or immature or inexperienced
the time of life between childhood and maturity
an early period of development