symbol

in quantities and units
https://doi.org/10.1351/goldbook.S06210
Conventional sign designating a quantity or a unit of measurement.
Notes:
  1. Symbols for quantities are denoted by letters of the Latin or Greek alphabet printed in italic (sloping) type; \(\text{pH}\) is an exception.
  2. Symbols for units are denoted by letters of the Latin or Greek alphabet printed in roman (upright) type.
Source:
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 995 (https://doi.org/10.1351/pac199668040957)