Injector for injecting fluid with - a valve assembly comprising a valve body and a valve needle, the valve body having a longitudinal axis and comprising a cavity with a valve seat, the valve needle comprising an armature retainer, being coupled in a fixed way to the valve needle and comprising an armature retainer constriction surface, the cavity being operable to take in the valve needle, the cavity and the valve needle being operable to prevent in a closing position of the valve needle, in which the valve needle is seated on the valve seat, an injection of fluid from the cavity to external to the injector, and to enable the injection of fluid when the valve needle is apart from the closing position, - an electromagnetic actuator assembly, which is operable to exert a force for influencing a position of the valve needle, comprising a pole piece and an armature, the pole piece being received in the cavity, being positionally fix with the valve body and comprising a pole piece constriction surface facing towards the armature, the armature being received in the cavity, operable to be axially displaced relative to the pole piece and to take along the armature retainer when being displaced towards the pole piece, characterized in that - a fluid channel through which fluid which enters the cavity at a fluid inlet end of the valve body and flows to a fluid outlet end of the valve body where the valve seat is positioned has to pass is defined by the armature retainer constriction surface and the pole piece constriction surface and - a first damping force is exerted on the valve needle by means of a hydraulic diameter of said fluid channel being at least twice as large when the valve needle is in the closing position compared to the hydraulic diameter when the valve needle is at a maximum displacement away from the closing position. - a valve assembly comprising a valve body and a valve needle, the valve body having a longitudinal axis and comprising a cavity with a valve seat, the valve needle comprising an armature retainer, being coupled in a fixed way to the valve needle and comprising an armature retainer constriction surface, the cavity being operable to take in the valve needle, the cavity and the valve needle being operable to prevent in a closing position of the valve needle, in which the valve needle is seated on the valve seat, an injection of fluid from the cavity to external to the injector, and to enable the injection of fluid when the valve needle is apart from the closing position, - an electromagnetic actuator assembly, which is operable to exert a force for influencing a position of the valve needle, comprising a pole piece and an armature, the pole piece being received in the cavity, being positionally fix with the valve body and comprising a pole piece constriction surface facing towards the armature, the armature being received in the cavity, operable to be axially displaced relative to the pole piece and to take along the armature retainer when being displaced towards the pole piece, characterized in that - a fluid channel through which fluid which enters the cavity at a fluid inlet end of the valve body and flows to a fluid outlet end of the valve body where the valve seat is positioned has to pass is defined by the armature retainer constriction surface and the pole piece constriction surface and - a first damping force is exerted on the valve needle by means of a hydraulic diameter of said fluid channel being at least twice as large when the valve needle is in the closing position compared to the hydraulic diameter when the valve needle is at a maximum displacement away from the closing position.