Propensity :: Propensity (n.) The quality or state of being propense; natural inclination; disposition to do good or evil; bias; bent; tendency.
Propenyl :: Propenyl (n.) A hypothetical hydrocarbon radical, C3H5, isomeric with allyl and glyceryl, and regarded as the essential residue of glycerin. Cf. Allyl, and Glyceryl..