thermal spring vs outflow

thermal spring and outflow both are nouns.

Word	Noun	Adjective	Verb	Adverb
thermal spring	Yes	No	No	No
outflow	Yes	No	No	No

As nouns, outflow is a hypernym of thermal spring; that is, outflow is a word with a broader meaning than thermal spring:

Other hypernyms of thermal spring include fountain, natural spring, outpouring, spring.

thermal spring (noun)	outflow (noun)
a natural spring of water at a temperature of 70 F or above	the discharge of a fluid from some container
	a natural flow of ground water
	the process of flowing out