How is the clavichord connected to the monochord?

The clavichord is considered a direct evolutionary descendant of the monochord, a scientific and musical instrument consisting of a string stretched over a sound box that was historically used to measure musical intervals.12

The connection between the two is rooted in their shared mechanical principles. The monochord utilized a movable bridge to divide a string into specific lengths to produce different pitches. The clavichord evolved by applying a keyboard mechanism to this concept: instead of manually moving a bridge, a player uses keys equipped with metal blades called tangents. When a key is pressed, the tangent strikes the string and simultaneously acts as a bridge, determining the string's sounding length by dividing it at a specific point.1234

Because of this close technical kinship, the two instruments were historically linked in terminology as well; as late as the 16th century, clavichords were frequently referred to as monocordia. Over time, the design progressed from using a few strings shared by multiple keys to the "unfretted" style, which eventually provided a dedicated pair of strings for every key.124