physics vs cryogenics

physics and cryogenics both are nouns.

Word	Noun	Adjective	Verb	Adverb
physics	Yes	No	No	No
cryogenics	Yes	No	No	No

As nouns, cryogenics is a hyponym of physics; that is, cryogenics is a word with a more specific, narrower meaning than physics:

physics: the science of matter and energy and their interactions
cryogenics: the branch of physics that studies the phenomena that occur at very low temperatures

physics (noun)	cryogenics (noun)
the science of matter and energy and their interactions	the branch of physics that studies the phenomena that occur at very low temperatures
the physical properties, phenomena, and laws of something