English has four open word classes: nouns, verbs, adjectives and adverbs. The reliable way to tell them apart is a slot test rather than a meaning test — a noun fits “the ___ is here”, a verb fits “they ___ed yesterday”, an adjective fits “a very ___ thing”, an adverb fits “she did it ___”. Meaning-based definitions fail immediately: “arrival” is a noun and it is not a person, place or thing.
Four classes, and the ones that are missing
This dictionary records four parts of speech: 117,953 noun entries, 21,499 adjective entries, 11,540 verb entries and 4,475 adverb entries. Those add to 155,467 across only 147,478 entries, because a great many words belong to more than one class.
They are the four open classes — open because new members join constantly. English gained new nouns and verbs this year and will gain more next year. What is missing is the closed classes: determiners (the, a, this), prepositions (of, in, between), pronouns (she, which), conjunctions (and, because) and auxiliaries (have, will). They are missing because WordNet is a database of lexical meaning, and those words do grammatical work rather than carrying a meaning you could gloss.
That is a real limit and worth stating plainly. If you look up “the” here you will not find a determiner entry, and that is not an oversight in the corpus — it is the boundary of what the corpus is for.
Why meaning-based definitions fail
The school definition — a noun is a person, place or thing — collapses on contact with ordinary English. Arrival is not a thing. Honesty is not a thing. The running of the race is not a thing. All three are nouns.
It fails in the other direction too. “Sleep” names an activity, which sounds verb-like, but “a good sleep” shows it is also a noun. Meaning does not determine class, because the same meaning can be packaged in any class: destroy, destruction, destructive, destructively all describe one event.
What a part of speech actually is, is a statement about distribution — which slots in a sentence a word can occupy. So the test that works is a slot test.
The frame test
Put the word in the frame. If it fits without the sentence going strange, it belongs to that class. Try each frame in turn; a word that fits several belongs to several.
| Class | Frame | Extra check |
|---|---|---|
| Noun | The ___ is here. / I saw a ___. | Can it take a plural or a possessive? one dog, two dogs, the dog’s |
| Verb | They ___ every day. / They ___ed yesterday. | Can it take -ing and a past tense? running, ran |
| Adjective | It is a very ___ thing. | Can it compare? bigger, biggest — or “more careful” |
| Adverb | She did it ___. / It was ___ obvious. | Does it modify a verb, an adjective or another adverb? |
One word, several classes
This is normal, not exceptional. “Fast” is an adjective, a verb, an adverb and a noun in this corpus, across 15 senses. “Well” covers all four across 22. “Present” carries 18 senses spread over verb, noun and adjective.
Because of that, every word page here groups senses by part of speech instead of running them together in one numbered list. When you look up “light”, the six adjective senses are separated from the noun senses and the verb senses, so you can go straight to the class you meant rather than reading past 40 meanings you did not.
It also matters for pronunciation. A handful of two-syllable words shift their stress with their class — the noun REC-ord against the verb ruh-KAWRD, the noun OB-ject against the verb ob-JECT. Our transcription records one stress per entry, which is a real limitation on exactly these words, and the entry pages do not pretend otherwise.
Adverbs are the small class, and the leaky one
There are only 4,475 adverb entries here against 117,953 nouns — adverbs are by far the smallest of the four, and the class where the usual shortcut lets you down.
The shortcut is “-ly means adverb”. It is wrong in both directions. Friendly, lovely, likely and costly are adjectives ending in -ly. Fast, well, hard, straight and early are adverbs with no -ly at all: “drive fast”, “slept well”, “works hard”.
Run the frame test instead. “She did it friendly” fails; “she did it fast” works. The suffix is a hint, and the slot is the answer.
- friendly, lovely, costly, likely — adjectives, despite the -ly.
- fast, well, hard, straight, late, early — adverbs, without one.
- hardly is not the adverb of hard: “works hard” and “hardly works” mean opposite things.
Why any of this is worth knowing
Three practical payoffs. It tells you which senses of a long entry to read — knowing you want the verb “run” cuts a 57-sense entry down to something manageable. It tells you which synonyms are even candidates, because a synonym has to belong to the same class as the word it replaces. And it explains why a word feels wrong in a sentence when every individual word in it is correct.
It is also the layer beneath most grammar advice. “Do not use adverbs” is really advice about a distributional class; so is “nominalisation makes prose heavy”, which is a complaint about turning verbs into nouns.
Questions
- How many parts of speech does English have?
- Traditionally eight or nine, but only four are open classes that gain new members: nouns, verbs, adjectives and adverbs. This dictionary records those four — 155,467 entries across the 147,478 in the corpus — because they are the classes that carry lexical meaning.
- Can a word be more than one part of speech?
- Constantly. The four class counts here add up to 155,467 across 147,478 entries, and the excess is words in more than one class. “Fast” is in all four.
- Is every word ending in -ly an adverb?
- No. Friendly, lovely, costly and likely are adjectives. And many common adverbs — fast, well, hard, straight — have no -ly. Use the frame test: an adverb fits “she did it ___”, an adjective fits “a very ___ thing”.
- Why can’t I find “the” or “because” in this dictionary?
- They are function words, and WordNet records lexical meaning rather than grammatical machinery. Determiners, prepositions, pronouns, conjunctions and auxiliaries are outside it. Every entry here belongs to one of the four open classes.