pycnometry vs mensuration

pycnometry and mensuration both are nouns.

Word	Noun	Adjective	Verb	Adverb
pycnometry	Yes	No	No	No
mensuration	Yes	No	No	No

As nouns, mensuration is a hypernym of pycnometry; that is, mensuration is a word with a broader meaning than pycnometry:

pycnometry: The determination of liquid density by weighing the liquid in a container (pycnometer) of known volume.
mensuration: the act or process of assigning numbers to phenomena according to a rule

Other hypernyms of pycnometry include measure, measurement, measuring.

pycnometry (noun)	mensuration (noun)
The determination of liquid density by weighing the liquid in a container (pycnometer) of known volume.	the act or process of assigning numbers to phenomena according to a rule