Hypoosmotic

Part of speech: adjective

Definitions

1. A solution that has a lower osmotic pressure than another solution, often causing water to move into it from a more concentrated solution
2. Referring to a condition where the solute concentration is less than that of another fluid, resulting in water migration
3. Describing a state in which the osmotic concentration is reduced compared to another solution, leading to cellular swelling from water influx

Etymology: Hypoosmotic is a plain technical formation: the prefix "hypo-", from Greek "hypo" meaning "under" or "below," attached to "osmotic." The base word itself comes from "osmosis," a term from the Greek "ōsmos," meaning "push" or "impulse," which describes the movement of a solvent across a membrane. Joining the two, "hypo-" signals a lower value on the scale that "osmotic" measures, namely osmotic pressure. The meaning therefore follows directly from the parts. A solution labelled hypoosmotic has less dissolved material than the solution it is being compared with, so water tends to pass into it across a semipermeable membrane. The same logic appears in the paired term "hyperosmotic," which uses the Greek prefix "hyper-" for "over" or "above."