optical density vs absorbance

optical density and absorbance both are nouns.

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

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

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

Other synonyms of optical density include photographic density, transmission density.

optical density (noun)	absorbance (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