AbstractAn extension of Bunn's nomenclature of polymer conformation is given with several examples. The structures of polyethers expressed by a general formula [(CH2)mO]nwithm= 1–4 are described and discussed with respect to the properties. Poly‐oxymethylene molecule has a helical structure which contains nine chemical units and five turns in the fiber identity period, and is the sequence of the internal rotation angle 78°13′. Detailed structure analysis of this polymer was made by the method of three‐dimensional Fourier synthesis. The diffraction data were measured on a highly ordered sample prepared from a single crystal of tetraoxymethylene by solid‐state radiation polymerization. It was deduced from the experimental results that the polyoxymethylene crystallite is composed of only one type of helix, either right‐handed or left‐handed. The poly(ethylene oxide) molecule is a loosely turned helix, and is a succession of nearlytrans, trans, andgaucheconformations. The structure of polytetrahydrofuran is essentially a planar zigzag. It has been also found quite recently that the third member, polyoxacyclobutane, has three types of crytalline modifications. One is planar zigzag, and the other two have longer fiber periods;T3GT3Ǧ and (T2G2)2types. The structure of polyallene [CH2C(CH2)]nis also discussed; this polymer is a succession of nearlygaucheconformations, the internal ro