Affinity
Etymology
From Latin affinitas "relationship by marriage," from affinis "bordering on, adjacent; related by marriage" (ad- "to" plus finis "border, end"). Two families joined by marriage shared a border — affinity is literally the state of bordering on, of adjoining. The surprise: it began as a legal term for in-law kinship.
noun · /uh-FIN-uh-tee/
A natural attraction or sense of likeness that draws you toward a person, group, or thing.
What it names
A handle for the pull of resemblance — the reason certain people, ideas, or aesthetics feel like "yours" without your having decided so.
Example
She felt an immediate affinity for the newcomer — the same dry humor, the same refusal to be impressed.
Related idea
Distinct from chemistry: affinity rests on perceived likeness or shared sensibility ("we are alike"), while chemistry is a raw spark that needs no basis and sometimes flares between opposites. Affinity explains itself; chemistry rarely can.