applicability
Refers to whether a rule, method, or principle can be applied to a particular case. Often used in technical, legal, or academic contexts.
We need to examine the applicability of this rule.
The applicability of the new treatment is confirmed through clinical trials.
応用 means practical application or putting theory to use, whereas 適用性 focuses on the suitability or relevance of an application.
Compound of 適用 (てきよう, 'application') and 性 (せい, '-ity, -ness'), forming a noun meaning 'applicability'.