One of the quantities that, in a system of quantities, are conventionally accepted as functionally independent of one another. In the SI, these are: @L03498@, @M03709@, @T06375@, @E01927@, @T06321@, @A00297@, and @L03647@. All other physical quantities (and units) are regarded as being derived from these base quantities (and @B00610@).
PAC, 1986, 58, 1405. (Recommendations for the presentation of thermodynamic and related data in biology (Recommendations 1985)) on page 1406 [Terms] [Paper]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 963 [Terms] [Paper]