serum

https://doi.org/10.1351/goldbook.ST06843
  1. Watery proteinaceous portion of the blood that remains after clotting. Synonym: blood serum
  2. Clear watery fluid especially that moistening the surface of serous membranes or that exuded through inflammation of any of these membranes.
Source:
PAC, 2004, 76, 1033. 'Glossary of terms used in toxicokinetics (IUPAC Recommendations 2003)' on page 1070 (https://doi.org/10.1351/pac200476051033)