central nervous system vs CNS

central nervous system and CNS both are nouns.

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

As nouns, central nervous system and CNS are synonyms defined as:

central nervous system and CNS: the portion of the vertebrate nervous system consisting of the brain and spinal cord

Other synonyms of central nervous system include systema nervosum centrale.

central nervous system (noun)	CNS (noun)
the portion of the vertebrate nervous system consisting of the brain and spinal cord	the portion of the vertebrate nervous system consisting of the brain and spinal cord