coefficient of drag vs drag coefficient

coefficient of drag and drag coefficient both are nouns.

Word	Noun	Adjective	Verb	Adverb
coefficient of drag	Yes	No	No	No
drag coefficient	Yes	No	No	No

As nouns, coefficient of drag and drag coefficient are synonyms defined as:

coefficient of drag and drag coefficient: the ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body

coefficient of drag (noun)	drag coefficient (noun)
the ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body	the ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body