Crystalloid

Part of speech: noun, adjective

Definitions

1. A substance that dissolves into a true solution and passes readily through a membrane ; a clear salt or electrolyte liquid given intravenously to replace fluid ; describing something with an orderly crystal-like internal structure
2. A material that forms a true solution and diffuses easily through a semipermeable barrier ; a clear, electrolyte-rich fluid administered into a vein to restore volume ; relating to a substance whose particles are arranged in a crystal-like pattern
3. Any substance whose molecules disperse evenly in solution and can cross a membrane ; a transparent saline fluid infused into the bloodstream during treatment ; having the regular, crystalline form typical of crystals

Etymology: "Crystalloid" is a compound built from "crystal" and the suffix "-oid", which comes from Greek "eidos" meaning "form" or "resemblance," so the word literally means "crystal-like." The pairing points to a meaning that has changed in ways a chemist would find useful: in ordinary speech a crystalloid is something resembling a crystal, but in medicine and chemistry it names a substance that dissolves into true solution and forms crystals, or passes freely through a membrane. The distinction matters most in medicine. Crystalloid fluids, such as saline solutions, are water with dissolved salts and small molecules, and they are contrasted with colloids, which contain larger particles suspended in the liquid. The word was coined to name this physical property rather than to describe a crystal's appearance, so the most common use today has little visible resemblance to a crystal at all.

Synonyms: crystalline

Antonyms: colloid