A lot vs. Alot: 9 Grammatical Pitfalls
early 15c., "watery," later "of or pertaining to serum" (16c.), from French séreux (16c.) and directly from Latin serosus, from serum "watery fluid, whey" (see serum). Related: Serosity.
serous se·rous (sēr'əs)adj. Containing, secreting, or resembling serum.