immediateness vs instantaneousness

immediateness and instantaneousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
immediateness	Yes	No	No	No
instantaneousness	Yes	No	No	No

As nouns, immediateness and instantaneousness are synonyms defined as:

immediateness and instantaneousness: the quickness of action or occurrence

Other synonyms of immediateness include immediacy, instancy.

immediateness (noun)	instantaneousness (noun)
the quickness of action or occurrence	the quickness of action or occurrence
lack of an intervening or mediating agency