Attribute of a phenomenon, body or substance that may be distinguished qualitatively and determined quantitatively.
  1. The term quantity may refer to a quantity in a general sense, for example length, mass, or to a particular quantity, for example length of a particular rod, mass of a specified object.
  2. The term @[email protected] refers to the abstract concept of a quantity common to a group of related quantities.
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 987 [Terms] [Paper]