optic chiasm vs chiasm

optic chiasm and chiasm both are nouns.

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

As nouns, chiasm is a hypernym of optic chiasm; that is, chiasm is a word with a broader meaning than optic chiasm:

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

Other hypernyms of optic chiasm include chiasma, decussation.

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