apo- in carotenoid nomenclature

in carotenoid nomenclature
https://doi.org/10.1351/goldbook.A00416
An unitalicized prefix, preceded by a locant, used to indicate that all of the molecule beyond the carbon atom corresponding to that locant has been replaced by hydrogen atoms.
Source:
White Book, 2nd ed., p. 230 [Terms] [Book]