essential basic and fundamental; "the essential feature"
dispensable capable of being dispensed with or done without; "dispensable items of personal property"
expendable (used of funds) remaining after taxes; "spendable income"
extrinsic not forming an essential part of a thing or arising or originating from the outside; "extrinsic evidence"; "an extrinsic feature of the new building"; "that style is something extrinsic to the subject"; "looking for extrinsic aid"