chiasm vs optic chiasm

chiasm and optic chiasm both are nouns.

Word	Noun	Adjective	Verb	Adverb
chiasm	Yes	No	No	No
optic chiasm	Yes	No	No	No

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

chiasm: an intersection or crossing of two tracts in the form of the letter X
optic chiasm: the crossing of the optic nerves from the two eyes at the base of the brain

Other hyponyms of chiasm include chiasma opticum, optic chiasma.

chiasm (noun)	optic chiasm (noun)
an intersection or crossing of two tracts in the form of the letter X	the crossing of the optic nerves from the two eyes at the base of the brain