Word classes: form-class and structure words
Form-class words (noun, verb, adjective, adverb) and structure words (determiners, auxiliaries, prepositions, conjunctions, pronouns, qualifiers, particles), the inflectional, derivational and positional tests, and words that change class.
Sorting the words of English
Every English sentence is built from words that do different jobs. In The tired teacher quickly checked the papers, some words carry the content (tired, teacher, quickly, checked, papers) and some hold the sentence together (the). Word classes, the traditional parts of speech, are the groups that words fall into by the way they behave. Knowing the class of a word lets you predict its endings, where it can stand, and which errors a learner is making.
- Form-class words – nouns, verbs, adjectives and adverbs: large, open classes that carry most of the meaning and change form.
- Structure words – determiners, auxiliaries, prepositions, conjunctions, pronouns, qualifiers and similar small, closed classes that signal grammatical relationships.
- Open / closed class – a class that readily takes new members / one that almost never does.
- Inflectional, derivational and positional tests – three ways to tell the class of a word: by its endings, by its suffixes and by the slots it fills in a sentence frame.
1. Two large groups
Structural grammarians such as Charles Fries and W. Nelson Francis divided English words into two groups, and the division is still the clearest way to start.
| Form-class words | Structure words | |
|---|---|---|
| Members | noun, verb, adjective, adverb | determiner, auxiliary, preposition, conjunction, pronoun, qualifier, interjection, particle |
| Size | thousands of words | a few hundred at most |
| New words | added every year (selfie, unfriend, presidentiable) | almost never added |
| Meaning | lexical meaning: things, actions, qualities | grammatical meaning: relations between other words |
| Form | take inflections and derivational suffixes | mostly do not change form |
| Other names | content words, lexical words, open class | function words, grammatical words, closed class |
Read a telegram-style headline such as Typhoon hits Samar, thousands evacuate: almost every structure word is gone and the message survives. Remove the form-class words instead (the … of the … in …) and nothing is left to understand.
2. Why the old definitions fail
School grammar defines a noun as "the name of a person, place or thing" and a verb as "an action word". These meaning-based definitions break down quickly. Arrival, destruction and swimming (in Swimming is fun) name actions, yet they are nouns. Be, seem and own are verbs, yet they name no action. Linguists therefore classify words by form and position, which can be checked, and use meaning only as a hint.
3. Telling the form classes apart
The inflectional test
English has only eight inflectional suffixes, and each form class takes its own set.
| Class | Inflections it can take | Example |
|---|---|---|
| Noun | plural -s, possessive -'s | student, students, student's |
| Verb | third person -s, past -ed, present participle -ing, past participle -en/-ed | walks, walked, walking; write, written |
| Adjective | comparative -er, superlative -est | tall, taller, tallest |
| Adverb | a few take -er/-est | soon, sooner, soonest; fast, faster |
The derivational test
Derivational suffixes usually mark the class of the new word: -ness, -ment, -tion, -ity make nouns (kindness, payment); -ize, -ify, -en make verbs (modernize, simplify, widen); -ous, -ful, -able, -ive make adjectives (dangerous, helpful); and -ly added to an adjective makes an adverb (quick → quickly). The test is a hint, not a proof: friendly and lovely end in -ly but are adjectives.
The positional (frame) test
A word that fits a slot in a test frame belongs to that class.
- Noun: The ______ seems good. (The plan seems good.) Nouns also follow a determiner: a ______, the ______.
- Verb: Let's ______ (it). (Let's start. Let's sing it.)
- Adjective: The ______ man seems very ______. (The old man seems very old.) Only an adjective fills both slots.
- Adverb: The man told his story ______. (quickly, there, yesterday)
4. The structure words
- Determiners come before a noun and its adjectives and limit it: articles (a, an, the), demonstratives (this, that, these, those), possessives (my, your, their) and quantifiers (some, every, each, no, many).
- Auxiliaries come before a main verb: be (is writing), have (has written), do (Did you write?) and the modals (can, could, may, might, must, shall, should, will, would).
- Prepositions take a noun phrase as their object and link it to the rest of the sentence: in, on, at, of, by, with, until, because of, in spite of.
- Conjunctions join. Coordinating conjunctions join equal parts (and, but, or, nor, for, so, yet); subordinating conjunctions introduce a dependent clause (because, although, if, when, until, that).
- Pronouns stand for a noun phrase: personal (I, she, them), demonstrative (this, those), indefinite (everyone, nothing), interrogative and relative (who, which), reflexive (herself).
- Qualifiers (intensifiers) modify an adjective or adverb: very, rather, quite, too, so (very tall, rather slowly).
- Particles join a verb to make a phrasal verb: up in look up the word, off in turn off the light. A particle can move after the object (look the word up); a preposition cannot (*look the hill up for look up the hill).
- Interjections stand outside the sentence's grammar: wow, oh, ouch, hey.
5. One word, several classes
A word's class is decided by how it is used in a particular sentence, not by the word on its own.
| Word | Sentence | Class |
|---|---|---|
| round | The boxer won the first round. | noun |
| The drivers round the corner slowly. | verb | |
| She has a round face. | adjective | |
| The children gathered round. | adverb | |
| The store is round the corner. | preposition | |
| that | That bag is mine. | determiner |
| I'll take that. | pronoun | |
| I know that he left. | conjunction | |
| until | We waited until noon. | preposition (object: noon) |
| We waited until the rain stopped. | conjunction (introduces a clause) |
Adjectives can also head a noun phrase when they refer to a group of people: The poor need help, The young are impatient. Poor is still an adjective (the very poor), used as the head of a noun phrase.
6. Notes for Filipino learners
- Count and noncount nouns. Information, equipment, furniture, advice, baggage and evidence are noncount in standard English, so *informations, *equipments and *an advice are errors. Use a piece of advice, some equipment.
- Pronoun gender. Tagalog siya and Cebuano siya cover both he and she, so learners may say *My mother, he is a nurse. English marks gender only in the third person singular.
- Articles. Filipino ang and ng do not match a and the one to one, so articles are often dropped (*She is teacher) or added (*the nature is beautiful, for nature in general).