A sliding door or window of the type comprising: - at least one fixed frame; - at least one openable sash; - at least one sliding unit interacting between the fixed frame and the openable sash in such a way as to enable the latter to slide in both directions (58, 59) along a horizontal line; - a control element associated with the sash and connected to operating means designed to set the sash from a condition in which it can slide to a condition in which the door/window can be locked, and vice versa; - an operating member or handle comprising a handle body that can be recessed, through a slot, in a cavity in the sash, the operating member further comprising: - a slider that can move forward and backward alternately in a guide in the handle body and connected to the controlling element in order to actuate the controlling element itself; and - a lever interpivoted to the handle body, characterized in that the lever is interpivoted to the handle body at fulcrum, in such a way as to form a first-class lever; the lever having a first end for gripping and a second operating end which can be conjugated with the slider that is operatively configured in such a way as to allow the lever to rotate between two stable limit conditions: a first condition in which the operating end applies with a first zone of it an opposing action on a first control profile of the slider, in such a way as to prevent translation of the slider when the lever is housed inside the handle body; and a second condition in which the operating end applies with a second zone of it a pushing action on a second control profile of the slider, opposite the first profile, in order to enable translation of the sash when the lever protrudes from the handle body. - at least one fixed frame; - at least one openable sash; - at least one sliding unit interacting between the fixed frame and the openable sash in such a way as to enable the latter to slide in both directions (58, 59) along a horizontal line; - a control element associated with the sash and connected to operating means designed to set the sash from a condition in which it can slide to a condition in which the door/window can be locked, and vice versa; - an operating member or handle comprising a handle body that can be recessed, through a slot, in a cavity in the sash, the operating member further comprising: - a slider that can move forward and backward alternately in a guide in the handle body and connected to the controlling element in order to actuate the controlling element itself; and - a lever interpivoted to the handle body, characterized in that the lever is interpivoted to the handle body at fulcrum, in such a way as to form a first-class lever; the lever having a first end for gripping and a second operating end which can be conjugated with the slider that is operatively configured in such a way as to allow the lever to rotate between two stable limit conditions: a first condition in which the operating end applies with a first zone of it an opposing action on a first control profile of the slider, in such a way as to prevent translation of the slider when the lever is housed inside the handle body; and a second condition in which the operating end applies with a second zone of it a pushing action on a second control profile of the slider, opposite the first profile, in order to enable translation of the sash when the lever protrudes from the handle body. a first condition in which the operating end applies with a first zone of it an opposing action on a first control profile of the slider, in such a way as to prevent translation of the slider when the lever is housed inside the handle body; and a second condition in which the operating end applies with a second zone of it a pushing action on a second control profile of the slider, opposite the first profile, in order to enable translation of the sash when the lever protrudes from the handle body.