convertible vs sofa bed

convertible and sofa bed both are nouns.

Word	Noun	Adjective	Verb	Adverb
convertible	Yes	Yes	No	No
sofa bed	Yes	No	No	No

As nouns, convertible and sofa bed are synonyms defined as:

convertible (noun)	sofa bed (noun)
a car that has top that can be folded or removed	a sofa that can be converted into a bed
a sofa that can be converted into a bed
a corporate security (usually bonds or preferred stock) that can be exchanged for another form of security (usually common stock)

convertible (adjective)	sofa bed (adjective)
capable of being exchanged for or replaced by something of equal value
designed to be changed from one use or form to another
capable of being changed in substance as if by alchemy