The quality or condition of being applicable; the degree to which something is relevant or suitable for a particular purpose or situation.
From 'applicable' (Latin 'applicabilis' from 'applicare') plus '-ity' (suffix forming abstract nouns). Standard formation in English from Latin-derived adjectives.
In business and law, 'applicability' became essential jargon—it's the noun version of asking 'does this rule apply to us?'—and it mattered so much it drove out older alternatives!
Complete word intelligence in one call. Free tier — 50 lookups/day.