A valve has a valve housing with a valve seat and a valve body holder with a fluid-permeable flow opening. A valve body is arranged in the valve body holder and axially displaceable between an open state and a closed state of the valve. The valve body has an envelope surface with a sealing region for fluid-tightly contacting the valve seat in the closed state. It has a base region adjoining the sealing region in longitudinal direction. A cross section contour of the envelope surface increases monotonously from the sealing region to the base region. In the open state, an axial end of the base region contacts the valve body holder. The envelope surface has a weakened region connecting sealing region and base region to each other. The weakened region has a reduced stiffness along the longitudinal direction. The valve body is formed of a thermoplastic polyhalogen olefin.