optical density vs transmission density

optical density and transmission density both are nouns.

Word	Noun	Adjective	Verb	Adverb
optical density	Yes	No	No	No
transmission density	Yes	No	No	No

As nouns, optical density and transmission density are synonyms defined as:

optical density and transmission density: (physics) a measure of the extent to which a substance transmits light or other electromagnetic radiation

Other synonyms of optical density include absorbance, photographic density.

optical density (noun)	transmission density (noun)
(physics) a measure of the extent to which a substance transmits light or other electromagnetic radiation	(physics) a measure of the extent to which a substance transmits light or other electromagnetic radiation