A Concise Guide to English Grammar

English words fall into two broad categories: open classes and closed classes. This chapter focuses on open classes; Chapter 6 addresses closed classes.

Open classes are word categories that readily accept new members. English speakers regularly create new nouns, verbs, adjectives, and adverbs:

These four classes—nouns, verbs, adjectives, and adverbs—contain the vast majority of English words and carry most of the content meaning in sentences. They are sometimes called content words or lexical words.

The openness of these classes tells us something profound about language: it’s creative. We don’t memorize a fixed list of nouns and then stop—we keep making new ones. When Bitcoin emerged, English speakers immediately needed a word, and “cryptocurrency” was coined. When a new social platform appeared, “tweet” became both a noun and a verb.

This creativity follows rules. We don’t randomly string sounds together; we use the morphological patterns from Chapter 4. A new noun meaning "one who podcasts" naturally becomes “podcaster”, following the same pattern that gave us “teacher” and “writer” centuries ago.

Understanding open classes helps you:

Each open class has characteristic morphological properties (what endings the word can take) and syntactic properties (how the word behaves in sentences). The following sections examine each class in detail, providing tests you can use to identify membership and explaining how each class builds phrases.