Open Class Words in English

Glossary of Grammatical and Rhetorical Terms

open-class words
The category of open-class words overlaps with the category of content words. M. Lynne Murphy notes that the open classes "are marked by the range and richness of the meanings they encode" ( Lexical Meaning, 2010). (Gregor Schuster/Getty Images)

In English grammar, open class refers to the category of content words—that is, parts of speech (or word classes) that readily accept new members. Contrast with closed class.

The open classes in English are nouns, lexical verbs, adjectives, and adverbs.

Research supports the view that open-class words and closed-class words play different roles in sentence processing.   

Examples and Observations

  • "All the words in a language can be broadly divided into two categories, open and closed. The closed category is so called because it does not easily accept new words. Its members are fixed and do not usually change . . .. The open category . . . contains nouns, verbs, adverbs, and descriptive adjectives--exactly those parts of speech that remain open to new additions . . ..

    "Words in the open category are usually further divided into simple and complex words. Simple words contain just one morpheme (house, for example, or walk, slow, or green), whereas complex words contain more than one (houses, walking, slowly, or greenest)."
    (Thomas E. Murray, The Structure of English. Allyn and Bacon, 1995)
  • Open-Class Words in Telegraphic Speech
    "Examples of open-class words are those belonging to the major part-of-speech classes (nouns, verbs, adjectives, and adverbs), which in any language tend to be quite large and 'open-ended.' that is, an unlimited number of new words can be created and added to these classes. . . .

    "One familiar variety of language in which the distinction between open-class words and closed-class words is important is known as telegraphic speech. The term telegraphic derives from the kind of language used in telegrams, where considerations of space (and money) force one to be as terse as possible. HAVING WONDERFUL TIME; HOTEL GREAT; RETURNING FLIGHT 256; SEND MONEY; STOP. Generally speaking, in telegraphic forms of language the open-class words are retained, whereas the closed-class words are omitted wherever possible."
    (Adrian Akmajian, et al., Linguistics: An Introduction to Language and Communication. MIT, 2001)
  • Open Class Words ↔ Closed Class Words
    "[O]pen-class words can evolve into grammatical words over time ('grammaticalization'). It is an essential part of the dictionary's task to describe this evolution. For example the verb ought (ought v.) has evolved from being the past tense of to owe to the condition of a pure auxiliary. Moreover, open-class words can develop senses that constitute fully grammaticalized lexical items, while retaining their original character in their other senses. For example, the verb to let (OED let v.1), the original meaning of which is 'leave' or 'allow to pass' (Branch I), and which retains a number of lexical meanings, developed in Middle English and still has an imperative auxiliary use with the infinitive (let us go). Or an inflected form of an open-class word may develop an independent use as a grammatical word, for example the conjunction providing. Additionally, grammatical words can develop from compounds that start out as straightforward syntactic constructions: for example, as and also from all so."
    (Edmund Weiner, "Grammatical Analysis and Grammatical Change." The Oxford Handbook of Lexicography, ed. by Philip Durkin. Oxford University Press, 2015)

    Other Relevant References