• Looked at in isolation, adjectives have several typical characteristics.
1. they often have suffixes which occur only with adjectives, for example: -ible (visible); -ful (careful); -ic (toxic); -ous (mountainous)
2. short adjectives can be inflected to create comparative and superlative forms, for example: clean, cleaner, cleanest
3. many adjectives act as a base from which adverbs can be created by adding ly, for example: thin → thinly; intelligent → intelligently
• Such characteristics cannot, however, provide a definition of the term “adjective”: most common adjectives do not have suffixes of any sort; adjectives of more than two syllables do not inflect to create comparatives and superlatives ; and, there are many adjectives that do not form the base of a -ly adverb.
• Adjectives operate as the headwords of adjective phrases and are very often their unitary constituents. By considering how these adjective phrases work — within noun phrases and as clause elements — it is possible to get a clearer idea of what adjectives are:
1. they are used attributively — i.e. they can “premodify” a noun by being placed immediately before it
2. they are used predicatively— i.e. they can be used as subject complements (following a “copular” verb, or as object complements)
3. they can be modified by “very”
4. they can have comparative and superlative forms (formed with suffixes or with “more,” “most,” “less,” or “least” as pre-modifiers)
• Many “central” adjectives — flat, smooth, beautiful, noisy, for example — have all four of these characteristics, but there are many others which lack one or more: A quite large group of adjectives beginning with the letter “a” — asleep, afraid, ashamed, for example — cannot be used attributively; nor can they be modified by the adverb, very.
• Nouns are often used attributively (i.e. before a noun) as in a metal door, a job application, a house party. When they are used this way, nouns satisfy the first of the four criteria for adjectives, but they do not satisfy any of the others and are not considered to be adjectives.
• Participial adjectives are adjectives which have the same suffixes as the -ed and -ing participles of verbs, and in most cases these adjectives are derived from verbs. That they are not participles despite being indistinguishable from them in isolation is indicated by the fact that, unlike verbs, they can be modified by the adverb, very. In most cases, -ing adjectives have an active sense whereas -ed adjectives have a passive sense. Moreover, there is a quite large class of -ed adjectives, — talented and diseased, for example — which are not derived from verbs, and these do not have a passive sense.