Ceramides (N-acyl-sphingoid bases) are a major subclass of sphingoid base derivatives with an amide-linked fatty acid. The fatty acids are typically saturated or monounsaturated with chain lengths from 14 to 26 carbon atoms; the presence of a hydroxyl group on carbon 2 is fairly common. Ceramides are generally precursors of more complex sphingolipids. In the illustrated generalised structure, R(1) = OH, OX (where X = acyl, glycosyl, phosphate, phosphonate, etc.), or H.