serum
/ˈsɪərəm/noun
(pl. sera /-rə/ 或serums)［mass noun］
1- an amber-coloured, protein-rich liquid which separates out when blood coagulates血清。
1.1
- the blood serum of an animal, used especially to provide immunity to a pathogen or toxin by inoculation or as a diagnostic agent免疫血清。
词源
late 17th cent.: from Latin, literally 'whey'.