dichroism vs pleochroism

dichroism and pleochroism both are nouns.

Word	Noun	Adjective	Verb	Adverb
dichroism	Yes	No	No	No
pleochroism	Yes	No	No	No

As nouns, pleochroism is a hypernym of dichroism; that is, pleochroism is a word with a broader meaning than dichroism:

dichroism: pleochroism of a crystal so that it exhibits two different colors when viewed from two different directions
pleochroism: the phenomenon of different colors appearing when certain crystals are viewed from different directions

dichroism (noun)	pleochroism (noun)
pleochroism of a crystal so that it exhibits two different colors when viewed from two different directions	the phenomenon of different colors appearing when certain crystals are viewed from different directions