gravitational constant vs constant of gravitation

gravitational constant and constant of gravitation both are nouns.

Word	Noun	Adjective	Verb	Adverb
gravitational constant	Yes	No	No	No
constant of gravitation	Yes	No	No	No

As nouns, gravitational constant and constant of gravitation are synonyms defined as:

gravitational constant and constant of gravitation: (physics) the universal constant relating force to mass and distance in Newton's law of gravitation

Other synonyms of gravitational constant include G, universal gravitational constant.

gravitational constant (noun)	constant of gravitation (noun)
(physics) the universal constant relating force to mass and distance in Newton's law of gravitation	(physics) the universal constant relating force to mass and distance in Newton's law of gravitation