Letting formula_213, we make "V" a "k"["t"]-module. The structure theorem then says "V" is a direct sum of cyclic modules, each of which is isomorphic to the module of the form formula_214. Now, if formula_215, then such a cyclic module (for formula_216) has a basis in which the restriction of "f" is represented by a Jordan matrix. Thus, if, say, "k" is algebraically closed, then all formula_216's are of the form formula_218 and the above decomposition corresponds to the Jordan canonical form of "f".