Morphologically, most adjectives are gradable. That is, they express the grammatical category known as degree. The basic form of the adjective, which expresses a quality, is known as the positive degree. To express a greater intensity of one of two items, the comparative degree is used, either by adding the suffix –er or with the word more and the basic adjective. To express the greatest intensity among three or more items, the superlative degree is used, either with –est or most.
Gradable adjectives can be tested by adding the word very in front of them. Thus
(13) She is very slow
(14) *Very fools waste time.
(15) *He very adores her.
Some adjectives, however, describe an all-or-nothing state, and aren't gradable. The very test sounds rather odd with these words, as in
(16) ?They were very present at the assembly.
In such cases, the very test won't help us decide whether present is an adjective. Notice, however, that present does pass the other structural tests for an adjective given above. For example, it can appear after a linking verb like were:
(16b) They were present at the assembly.