different between validity vs rightfulness

English

valid +? -ity, borrowed from Middle French validité, from Late Latin validitas.

validity (countable and uncountable, plural validities)

The state of being valid, authentic or genuine.
State of having legal force.
A quality of a measurement indicating the degree to which the measure reflects the underlying construct, that is, whether it measures what it purports to measure (see reliability).

From Middle English ri?tfulnesse, rigtfulnes, ri?tvolnesse, equivalent to rightful +? -ness.

rightfulness (uncountable)

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