Adjectives typically specify characteristics of nouns, or they limit the application, as in "the large refund," "an enthusiastic participant," or "purple prose." Most often they appear before a noun, although they can also appear in their own phrases after certain verbs known as linking verbs, as in "Wilma looks cheerful." or "They were happy."

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.

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In terms of their distribution, verbs are words that can appear after auxiliaries. In the frame sentence (5), repeated for convenience, can is the auxiliary:

(5) She can ____.

We will have more to say about auxiliaries later. For now, we can simply note that they are words like can, could, will, would, shall, should, may, might, or must. In most grammar books, auxiliaries are considered a special type of verb, and that is how we will treat them. But it's important to note that auxiliaries do not behave like most other verbs. In particular, they fail most of the tests for verb-hood given here. For example, the frame sentence (5) cannot be filled in with another auxiliary.

Although I have already tried to show why the traditional definition of a noun (person, place, or thing) is inadequate, now that we have come to define what nouns are, I am going to start with that definition anyway. Am I contradicting myself? Not really. Nouns do refer to people, places, and things, but that doesn't exhaust the extent of their reference. People, places, and things are prototypical nouns. If we're studying a new language, the category that we will call "noun" in that language will be the one that includes these core objects.[1] We will start with these core nouns, observe the patterns that they exhibit, and then use those patterns as a structural test for other words whose category membership may be less clear.

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