In uncountable|lang=en terms the difference between extensivity and extensity
is that extensivity is (uncountable) the condition of being extensive while extensity is (uncountable) the state of being extensive or of having extension.
In countable|lang=en terms the difference between extensivity and extensity
is that extensivity is (countable) the extent to which something is extensive while extensity is (countable) the degree to which something is extensive.
As nouns the difference between extensivity and extensity
is that extensivity is (uncountable) the condition of being extensive while extensity is (uncountable) the state of being extensive or of having extension.
extensivity
English
Noun
(uncountable) The condition of being extensive
(countable) The extent to which something is extensive extensity
English
Noun
(uncountable) The state of being extensive or of having extension
(countable) The degree to which something is extensive