swan vs cygnet

swan and cygnet both are nouns.

Word	Noun	Adjective	Verb	Adverb
swan	Yes	No	Yes	No
cygnet	Yes	No	No	No

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

swan: stately heavy-bodied aquatic bird with very long neck and usually white plumage as adult
cygnet: a young swan

swan (noun)	cygnet (noun)
stately heavy-bodied aquatic bird with very long neck and usually white plumage as adult	a young swan

swan (verb)	cygnet (verb)
to declare or affirm solemnly and formally as true
move about aimlessly or without any destination, often in search of food or employment
sweep majestically