se·rum | \ ˈsir-əm \
plural sera\ ˈsir-ə \ or serums
[external_link_head] 1 : the watery, clear portion of an animal fluid: a : the clear, yellowish fluid that remains from blood plasma after clotting factors (such as fibrinogen and prothrombin) have been removed by clot formation : blood serum — compare antiserum , convalescent serum b : a normal or pathological serous fluid (as in a blister)
2 : a usually lightweight cosmetic preparation especially for use on the face specifically : a typically water-based, often concentrated preparation that lacks lubricating and thickening agents an antiaging facial serum
3 : the watery part of a plant fluid Latex. This, the natural product of the rubber tree, is a suspension of rubber droplets in a watery serum concentrated and stabilized in such a way that the dry rubber content is between 60 and 70 per cent.— C. A. O'Flaherty — see also truth serum
: occurring or found in the blood serum serum cholesterol serum antibodies
