hydrometer vs gravimeter

hydrometer and gravimeter both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydrometer	Yes	No	No	No
gravimeter	Yes	No	No	No

As nouns, hydrometer and gravimeter are synonyms defined as:

hydrometer and gravimeter: a measuring instrument for determining the specific gravity of a liquid or solid

hydrometer (noun)	gravimeter (noun)
a measuring instrument for determining the specific gravity of a liquid or solid	a measuring instrument for determining the specific gravity of a liquid or solid
	a measuring instrument for measuring variations in the gravitational field of the earth