If two terms are juxtaposed without a coordinator they need not be in asyndeton, though it is commonly assumed in commentaries that any juxtaposed words of the same part of speech must be asyndetic. There are various relationships between two words that may rule out the insertion of a coordinator. For example, if the two are adjectives, they may differ hierarchically (see e.g. Quirk et al. 1972: 550–1), a distinction sometimes referred to as ‘rank’. Or one may be attributive and the other predicative, or a secondary predicate (see below). A pair may form an ‘appositional compound’. Again, one term may be a modifier of the other, with overt coordination possibly unnecessary or inappropriate, though this type is rather nebulous. All these categories will be illustrated below. Perhaps most important are the roles of adjectives, such as attributive versus predicative. The distinction is sometimes neglected in literary commentaries.