Psychoactivity

Part of speech: noun

Definitions

1. The effect a substance or agent has on mental processes or behavior patterns
2. The capacity of a chemical or compound to alter perception, mood, consciousness, cognition, or behavior
3. The influence that an element exerts on brain function, resulting in changes to thought, mood, or actions

Etymology: "Psychoactivity" is a plain formation: it takes "psychoactive," itself built from "psycho-" (from Greek "psykhē," meaning soul, mind, or breath of life) and "active," and adds the English suffix "-ity," which turns an adjective into a noun meaning a quality or capacity. The result names the property of a substance rather than the substance itself, so a compound that alters the mind has psychoactivity in the same way a metal has conductivity. The sense of "active" here is the older one, "producing an effect," rather than "busy." That is why the word can describe something that is entirely still in a bottle yet has a pharmacological effect once it reaches the brain. The prefix carries its Greek meaning of mind or soul through the whole compound, even though modern usage has little to do with the soul.