x1 (ka) is specific/particular/specialized/[special]/a defining property of x2 among x3 (set).
[x2 are members/individuals of a subset of x3; object whose association is specific/defining of a subset or individuals (= tecra'a, also cf. cmavo list po'e, [x2 is also special to x1]); also: especially/strongly/specifically associated]; (x3 is completely specified set)]; See also srana, se ponse, ckini, tcila, tutra.