The actuator (1) has two single-piece segments (2, 3) that are adjustable along and/or over an actuatory axis (A). A pair of shape memory alloy elements (5, 7) is arranged between the segments and connected to the segments. The shape memory alloy elements are oppositely bent from each other. The segments are formed in same and/or identical shape such as polygon, box and/or tube shape. The segments are concentrically or coaxially arranged or arranged in a telescopic shape. The shape memory alloy elements are formed as a wire and/or band.