encephalon vs central nervous system

encephalon and central nervous system both are nouns.

Word	Noun	Adjective	Verb	Adverb
encephalon	Yes	No	No	No
central nervous system	Yes	No	No	No

encephalon (noun)	central nervous system (noun)
that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord	the portion of the vertebrate nervous system consisting of the brain and spinal cord