oblateness vs ellipticity

oblateness and ellipticity both are nouns.

Word	Noun	Adjective	Verb	Adverb
oblateness	Yes	No	No	No
ellipticity	Yes	No	No	No

As nouns, oblateness and ellipticity are synonyms defined as:

oblateness and ellipticity: the property possessed by a round shape that is flattened at the poles

oblateness (noun)	ellipticity (noun)
the property possessed by a round shape that is flattened at the poles	the property possessed by a round shape that is flattened at the poles