5.6 Prepositions 115 5.5 ADJECTIVES An adjective is a word that can be used as either 1. a pre-modifier of a noun (an attributive adjective), as in "checked bag", or 2. part of a predicate following a noun and the verb `is' (in which case it is a predicative adjective), as in "this bag is checked". For example, `international' can precede `flight' (as in "the international flight") or follow "flight is" (as in "this flight is international") and is therefore an adjective. Note that not all adjectives can be used in both ways. For example, `former' can only be used as an attributive adjective, as in "former employee" (we do not say "*the employee is former" 26 ). By con- trast, `well', when used as an adjective, can only be used predicatively: we can say "the patient is well" but not "*the well patient". The adjective `valid' has a special use in a standard format definition rules (see Section 4.9.1.7 in Chapter 4). Other adjectives may appear only in compound nouns (see Section 5.1.2) or compound verbs (see Section 5.3.3) in a fact type or rule statement.