Abstract: A polyetheric copolymer, a polyetheric block copolymer, and compositions of these copolymers containing:a benzonitrile recurring unit as represented by the following general formula (I): ##STR1## and a benzophenone recurring unit as represented by the following general formula (II): ##STR2## which copolymer has a molar ratio of the recurring unit (I) to a sum of the recurring units (I) and (II), i.e., (I)/[(I)+(II)], in the range from 0.15:1 to 0.40:1, as well as a melt viscosity (zero shear viscosity) at 400.degree. C. in the range from 500 to 100,000 poise.The polyetheric copolymer is crystalline and is a macromolecular compound having excellent heat resistance and mechanical strength.Disclosed herein are methods for the preparation of the polyetheric copolymer, the polyetheric block copolymer and the compositions containing the same.The polyetheric copolymers, the polyetheric block copolymers and their compositions are useful in various fields.