brain vs unconscious

brain and unconscious both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain	Yes	No	Yes	No
unconscious	Yes	Yes	No	No

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

brain: that which is responsible for one's thoughts, feelings, and conscious brain functions; the seat of the faculty of reason
unconscious: that part of the mind wherein psychic activity takes place of which the person is unaware

Other hyponyms of brain include noddle, tabula rasa, ego, unconscious mind, subconscious, subconscious mind.

brain (noun)	unconscious (noun)
that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord	that part of the mind wherein psychic activity takes place of which the person is unaware
mental ability
that which is responsible for one's thoughts, feelings, and conscious brain functions; the seat of the faculty of reason
the brain of certain animals used as meat
someone who has exceptional intellectual ability and originality

brain (adjective)	unconscious (adjective)
	not conscious; lacking awareness and the capacity for sensory perception as if asleep or dead
	without conscious volition
	(followed by `of') not knowing or perceiving

brain (verb)	unconscious (verb)
hit on the head
kill by smashing someone's skull