NOVELTY - Making a polyolefin fiber comprises: (A) providing at least one polyolefin tape; (B) twisting or folding the at least one polyolefin tape longitudinally to obtain a precursor fiber; and (C) exposing the precursor fiber under tension to a temperature within the melting point range of the polyolefin for a time sufficient to at least partly fuse two or more parts of the precursor fiber.    USE - The process is useful for making a polyolefin fiber (claimed).    ADVANTAGE - The shape of the cross section of a polyolefin tape allows twisting or folding of the tape in its longitudinal direction, and the material of the polyolefin tape allows fusing of the adjacent layers. Since the fiber is made from a tape or tapes that are inherently connective in the width direction, the fiber made by the process above has a more homogeneous structure and better integrity in its transverse direction compared to a fiber made from filaments having a circular cross section. The number of the tape required for making a fiber can be made smaller than when using precursor filaments having a generally circular cross section. The surface of the product may be made to have much less area of fused borders compared to a product made from multiple precursor filaments. The fused borders decrease the surface smoothness of the fiber. By adjusting the way in which the tape is twisted or folded and the fusing conditions such as temperature and pressure, the area of the fused borders on the surface, thus the surface roughness, of the fiber may be adjusted. It is advantageous, especially for use in a fishing line, that the surface roughness is low. During the reshaping of the tape into a fiber, the properties may even be improved. The polyolefin tape from which the fiber is made may not necessarily be made by a spinning process such as a gel-spinning process or a melt-spinning process. According to the present invention, it has been made possible to make a fiber without a spinning process. The fiber is made from one tape. The shape of the cross section of a polyolefin tape allows reshaping one single polyolefin tape into a fiber having e.g. a circular cross section. Such reshaping is not possible with a conventional fiber with a generally circular cross section. The structure of the resultant fiber is most homogeneous when it is made from one single tape.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a fiber obtainable by the process above, preferably having a substantially circular cross section; and    (2) a fishing line comprising the fiber of (1).