Unsaturation

Part of speech: noun

Definitions

1. The state in which a molecule contains multiple bonds, leading to a decrease in hydrogen atoms relative to its possible saturation level
2. A condition found in organic compounds where the presence of double or triple bonds results in fewer hydrogen atoms than could theoretically exist
3. The chemical condition where a molecule has one or more double or triple bonds, lowering the hydrogen content compared to a fully saturated counterpart

Etymology: "Unsaturation" is a chemistry term for a molecule that still has the capacity to form additional bonds, and it is built from two familiar English parts. The prefix "un-" is one of the oldest native elements in the language, inherited from Proto-Germanic and used in Old English to reverse or negate a quality. Attached to "saturation," it turns the idea of a fully filled state into its opposite. The base word "saturation" traces back to Late Latin "saturatio," a noun from the verb meaning to fill or satisfy, and it entered English as a borrowing that was later adopted into chemical vocabulary. Chemists used "saturated" to describe compounds whose atoms had bonded to all the hydrogen they could hold, so an "unsaturated" compound was one that could still take on more. The compound "unsaturation" simply names that condition as a noun, which is why it reads so plainly: the chemistry is spelled out in the word itself.