x1 and x2 are path-linked by binary predicate x3 (ka) via intermediate steps x4 (ce'o; (ordered) list).
For example, "lo stedu ku utka lo birka lo ka (ce'u ce'u) lamji" is true, with x4 equal to something like "lo cnebo ce'o lo cutne ce'o lo janco". (Also: "lo stedu ku lamji'utka lo birka".) Formally, "utka(A, B, P, [L1...L])" is equivalent to "P(A, L1) and P(L1, L and ... and P(L(n-1), L and P(Ln, B)". The x4 may be empty ("lo nomei") if there are no intermediate steps (id est: the relevant path-linking between x1 and x2 is direct). x4 is a list of only the intermediate steps between x1 and x2 and does not include x1 or x2 themselves; it is ordered so that the relevant relation (x3) holds between x1 and the first term/entry of the list (in that order), between each successive pair of consecutive terms/entries of the list (in the order in which they are listed), and between the last term/entry of the list and x2 (in that order). x4 may not be unique. x3 may not be symmetric (commutative) under exchange of its operands. The predicate may be asymmetrical. See also: ".efku", "ki'irsi", ".utka'au", "takni", "taknyklojyzilpra". See ".utkaro" and ".utkakpu" for somewhat stronger conditions.