pineal eye vs third eye

pineal eye and third eye both are nouns.

Word	Noun	Adjective	Verb	Adverb
pineal eye	Yes	No	No	No
third eye	Yes	No	No	No

As nouns, pineal eye and third eye are synonyms defined as:

pineal eye and third eye: a sensory structure capable of light reception located on the dorsal side of the diencephalon in various reptiles

pineal eye (noun)	third eye (noun)
a sensory structure capable of light reception located on the dorsal side of the diencephalon in various reptiles	a sensory structure capable of light reception located on the dorsal side of the diencephalon in various reptiles