Rank-order is a term used to denote a specific ordering of items, usually with respect to their perceived worth or value. Synonyms for the term include hierarchy, rating, classification, grading, order of preference, and arrangement. A hierarchy denotes a system of ranking in which the items are arranged in descending order of importance, power, or authority. A rating may refer to a numerical score assigned to an item to indicate its value or quality. Classification refers to the grouping of items based on their attributes. Grading usually pertains to the evaluation of quality of items based on specific criteria. Order of preference refers to the sequence in which items are arranged based on their desirability. Arrangement denotes the specific order in which items are enumerated or organized.