broth vs stock cube

broth and stock cube both are nouns.

Word	Noun	Adjective	Verb	Adverb
broth	Yes	No	No	No
stock cube	Yes	No	No	No

As nouns, stock cube is a hyponym of broth; that is, stock cube is a word with a more specific, narrower meaning than broth:

broth: liquid in which meat and vegetables are simmered; used as a basis for e.g. soups or sauces
stock cube: a cube of dehydrated stock

Other hyponyms of broth include liquor, pot likker, pot liquor, beef broth, beef stock, chicken broth, chicken stock.

broth (noun)	stock cube (noun)
a thin soup of meat or fish or vegetable stock	a cube of dehydrated stock
liquid in which meat and vegetables are simmered; used as a basis for e.g. soups or sauces