builder vs boatbuilder

builder and boatbuilder both are nouns.

Word	Noun	Adjective	Verb	Adverb
builder	Yes	No	No	No
boatbuilder	Yes	No	No	No

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

builder: someone who contracts for and supervises construction (as of a building)
boatbuilder: a person who builds boats

builder (noun)	boatbuilder (noun)
someone who contracts for and supervises construction (as of a building)	a person who builds boats
a person who creates a business or who organizes and develops a country
a substance added to soaps or detergents to increase their cleansing action