hydra vs problem

hydra and problem both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydra	Yes	No	No	No
problem	Yes	No	No	No

As nouns, problem is a hypernym of hydra; that is, problem is a word with a broader meaning than hydra:

hydra: trouble that cannot be overcome by a single effort because of its many aspects or its persistent and pervasive quality
problem: a source of difficulty

Other hypernyms of hydra include trouble.

hydra (noun)	problem (noun)
small tubular solitary freshwater hydrozoan polyp	a source of difficulty
trouble that cannot be overcome by a single effort because of its many aspects or its persistent and pervasive quality	a question raised for consideration or solution
	a state of difficulty that needs to be resolved