third eye vs pineal eye

third eye and pineal eye both are nouns.

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

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

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

third eye (noun)	pineal 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