The invention relates to an extruder screw comprising an extruder shaft and at least one extruder segment (10). The extruder shaft comprises a prismatic mandrel having external teeth and a longitudinal mandrel axis. The extruder segment (10) has internal teeth (12) and a longitudinal internal-teeth axis (L12) and can be slid onto the mandrel, such that the extruder segment (10) can be connected to the mandrel for rotation therewith. The internal teeth (12) have a profile having a meshing profile and, in an inner area between the first (16) and second (18) end faces of the extruder segment (10), comprise a prismatic main profile that has a main cross-section. Furthermore, the internal teeth (12) of the extruder segment (10) have an edge profile adjacent to at least one end face (16) of the extruder segment (10), which edge profile has a smaller edge cross-section than the main profile at least in the area of the meshing profile.