What the paragraph below is telling me is that a noun can be modified by only by an adjective or by other words.

The traditional definition of adjective is "a word that modifies a noun." Like the word adverb, however, adjective actually refers to a word class, or form, with particular characteristics, not to a grammatical function. That traditional definition, then, turns out to denote an adjectival, the topic of this chapter. By now you've probably come to understand that the adjective is only one of many structures that modify nouns. In this chapter, you'll examine other forms and structures that function as adjectivals.