1 A device for measuring portions of a total entity or the value of a specific quantity within a range covered by the measuring device. The measurement scale may be ordered, i.e., zero to infinity, or relative proportional. Many entities are measurable in biology, medicine, and public health (length, mass, pressure, time, radiation dose, etc.), and the instruments used to measure them all have some sort of scale. See also measurement scale for discussion of categories of scale.
2 The deposit of solid matter on the inside of boilers, kettles, etc.
3 Skin lesions with dried seborrheic exudate and/or horny excrescences on the skin.
4 The deposit of tartar compounds that collects on the teeth.