Sera

Part of speech: noun

Definitions

1. A stretchy attachment device designed for binding multiple items together
2. Fluids derived from blood that contain antibodies but no cells or clotting factors
3. Clear yellowish component separated from blood that plays a role in immune response

Etymology: "Sera" is the plural of "serum", so it refers to more than one kind of serum. The singular comes from Latin "serum", which meant "whey", the watery liquid that separates from milk when it curdles. That original sense explains the modern one: a serum is the thin, pale fluid left behind when blood clots, and the same word is used for the clear part of other body fluids. The Latin root traces back through Proto-Italic to the Proto-Indo-European "*ser-", a reconstructed root for the idea of liquid or whey, which passed into English unchanged in spelling. Related forms survive in several modern languages: French "sérum", Spanish "suero", Italian "siero" and "siero", and Portuguese "soro" all mean the same watery substance. Spanish "suero" is a doublet of the English word, meaning the two came into their languages from the same Latin source by different routes.