balsa raft vs raft

balsa raft and raft both are nouns.

Word	Noun	Adjective	Verb	Adverb
balsa raft	Yes	No	No	No
raft	Yes	No	Yes	No

As nouns, raft is a hypernym of balsa raft; that is, raft is a word with a broader meaning than balsa raft:

balsa raft: a light raft made of balsa
raft: a flat float (usually made of logs or planks) that can be used for transport or as a platform for swimmers

balsa raft (noun)	raft (noun)
a light raft made of balsa	a flat float (usually made of logs or planks) that can be used for transport or as a platform for swimmers
	a foundation (usually on soft ground) consisting of an extended layer of reinforced concrete
	(often followed by `of') a large number or amount or extent