A unit is a reference amount of a physical quantity used to measure quantities of the same dimensions. Each unit is represented by a tree node with properties; its pop-up menu consists of common menu items.
Examples of some standard units are meter, foot, second, kilogram, Newton, pound and Watt.
A unit has an associated set of dimensions. For example a meter has dimensions of length. A foot, inch and millimeter also have dimensions of length. Any quantity with dimensions of length can therefore be expressed in meters, feet, inches and millimeters. It is also possible to set preferred units.