validity; appropriateness; soundness
Refers to whether something is logically valid, reasonable, or appropriate in a given context. Often used in formal or technical discussions about arguments, methods, or decisions.
We need to verify the validity of that claim.
Let's discuss the appropriateness of this method.
正当性 implies moral or legal justification, whereas 妥当性 is more about logical or contextual appropriateness.
Compound of 妥当 (valid, appropriate) + 性 (-ness, -ity). The exact historical derivation is uncertain, but the kanji 妥 (gentle, peace) and 当 (hit, right) contribute to the meaning of something being fitting or proper.