fluidness vs runniness

fluidness and runniness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fluidness	Yes	No	No	No
runniness	Yes	No	No	No

As nouns, fluidness and runniness are synonyms defined as:

Other synonyms of fluidness include fluidity, liquidity, liquidness.

fluidness (noun)	runniness (noun)
the property of flowing easily	the property of flowing easily
a changeable quality