angle of extinction vs extinction angle

angle of extinction and extinction angle both are nouns.

Word	Noun	Adjective	Verb	Adverb
angle of extinction	Yes	No	No	No
extinction angle	Yes	No	No	No

As nouns, angle of extinction and extinction angle are synonyms defined as:

angle of extinction and extinction angle: the angle from its axis that a crystal must be rotated before appearing maximally dark when viewed in polarized light

angle of extinction (noun)	extinction angle (noun)
the angle from its axis that a crystal must be rotated before appearing maximally dark when viewed in polarized light	the angle from its axis that a crystal must be rotated before appearing maximally dark when viewed in polarized light