Interpreting SI notation for units and dimensions

An interpretation of the notation for unit symbols and dimensions is proposed that emphasises the role of unit symbols and dimensional terms in unit conversion. Dimensional terms can be understood as variables for conversion factors, and unit symbols as variables for conversion factors that are partially specified by standardised symbols. Adopting this view avoids semantic difficulties that arise when unit symbols are understood to refer to reference quantities of the same kind as the expressed quantity, and when dimensions are associated with quantities of the same kind. Providing distinct interpretations for notation and measurement will clarify the semantics of unit and dimensional notations.