b (1): an attraction to or liking for something <people with an affinity to darkness — Mark Twain><pork and fennel have a natural affinity for each other — Abby Mandel>(2): an attractive force between substances or particles that causes them to enter into and remain in chemical combination
c: a person especially of the opposite sex having a particular attraction for one
a: likeness based on relationship or causal connection <found an affinity between the teller of a tale and the craftsman — Mary McCarthy><this investigation, with affinities to a case history, a psychoanalysis, a detective story — Oliver Sacks>
b: a relation between biological groups involving resemblance in structural plan and indicating a common origin
He never felt any affinity with the other kids in his neighborhood.
Jefferson's personal debts continued to mount … . His addiction to French wine, like his affinity for French ideas, never came to grips with the more mundane realities. —Joseph J. Ellis, American Heritage, May/June 1993
… neither virus has an affinity for T cells. —Robert C. Gallo, Scientific American, 1987
Animals sharing this basic architecture may have no closer affinity than a beetle and a squid. —Stephen Jay Gould, Natural History, 1985