To improve thermal and mechanical properties by using a poly (etherimide) containing a unit having a special chemical structure.

A polyetherimide which is soluble in an organic solvent contains a unit of formula I wherein Ar2 is selected from the group consisting of 30 groups substantially represented by formula II, III or the like. This polyetherimide can be synthesized in a two-step process in which a ring opening polyaddition reaction of a bisether anhydride is conducted by using various aromatic diamines in a suitable solvent (DMAc or the like) to obtain a polyamic acid and chemical (addition of acetic anhydride and pyridine) or thermal cyclodehydration is conducted. Alternatively, it can be synthesized in a one-step process in which the two reactants, a bisether anhydride and an aromatic diamine, are directly heated in a high boiling point solvent (e.g. m-cresol). Preferably, the colorless polyetherimide is prepared by the two-step process and chemical cyclodehydration.