Rheos

Part of speech: noun

Definitions

1. The continuous movement or flow of a substance, especially fluids like water or air; the rate or manner in which something flows or runs; an electrical property describing resistance to alternating current
2. The steady passage or motion of liquid, gas, or electricity in a system; how quickly or smoothly a material moves along a path; a measure of a material's response to an electric current that changes direction
3. The act or condition of flowing in a stream or current; the velocity or character of flow within a channel; a concept in physics referring to electrical impedance to fluctuating currents

Etymology: In ancient Greek, "rheos" meant a flow or a stream, the movement of water or anything else that runs. It comes from the verb "rhein," "to flow," which traces back to a much older root meaning the same thing. English rarely uses the noun alone. It survives mainly as the combining form "rheo-," which scientists attached to Greek endings to name new ideas. The clearest example is "rheology," the study of how matter flows and deforms, built from "rheo-" and "-logy." Electrical engineers used the same prefix for devices that regulate current. A "rheostat" is a variable resistor that controls how much current flows through a circuit, joining "rheo-" to "-stat," from Greek "statos," meaning standing or stationary.