freeze-drying vs dehydration

freeze-drying and dehydration both are nouns.

Word	Noun	Adjective	Verb	Adverb
freeze-drying	Yes	No	No	No
dehydration	Yes	No	No	No

As nouns, dehydration is a hypernym of freeze-drying; that is, dehydration is a word with a broader meaning than freeze-drying:

freeze-drying: a method of drying food or blood plasma or pharmaceuticals or tissue without destroying their physical structure; material is frozen and then warmed in a vacuum so that the ice sublimes
dehydration: the process of extracting moisture

Other hypernyms of freeze-drying include desiccation, drying up, evaporation, freeze, freezing.

freeze-drying (noun)	dehydration (noun)
a method of drying food or blood plasma or pharmaceuticals or tissue without destroying their physical structure; material is frozen and then warmed in a vacuum so that the ice sublimes	the process of extracting moisture
	dryness resulting from the removal of water
	depletion of bodily fluids