Oh I just found this in the notes to {tarmi}.
x1 [ideal] is the conceptual shape/form of object/abstraction/manifestation x2 (object/abstract).
Also pattern; x1 is the mathematical or theoretical ideal form, while x2 is an object/event manifesting that form; e.g. circular/circle-shaped (= cukseltai) vs. circle (=cuktai, while cukla alone is ambiguous); model (= ci'ersaptai, saptai, ci'ersmitai, smitai). See alse nejni, te marji for physical shape, tapla, bliku, kubli, kurfa, cukla, mapti, morna, sarlu.
Why don't we have cukseltai and cuktai in jvs? What would it be their place structure?