Words are fundamental units in every sentence, so we will begin by looking at these. Consider the words in the following sentence:
My brother drives a big car.
We can tell almost instinctively that brother and car are the same type of word, and also that brother and drives are different types of words. By this we mean that brother and car belong to the same word class. Similarly, when we recognise that brother and drives are different types, we mean that they belong to different word classes. We recognise seven MAJOR word classes:
|Verb||be, drive, grow, sing, think|
|Noun||brother, car, David, house, London|
|Determiner||a, an, my, some, the|
|Adjective||big, foolish, happy, talented, tidy|
|Adverb||happily, recently, soon, then, there|
|Preposition||at, in, of, over, with|
|Conjunction||and, because, but, if, or|
You may find that other grammars recognize different word classes from the ones listed here. They may also define the boundaries between the classes in different ways. In some grammars, for instance, pronouns are treated as a separate word class, whereas we treat them as a subclass of nouns. A difference like this should not cause confusion. Instead, it highlights an important principle in grammar, known as GRADIANCE. This refers to the fact that the boundaries between the word classes are not absolutely fixed. Many word classes share characteristics with others, and there is considerable overlap between some of the classes. In other words, the boundaries are «fuzzy», so different grammars draw them in different places.
We will discuss each of the major word classes in turn. Then we will look briefly at some MINOR word classes. But first, let us consider how we distinguish between word classes in general.
Criteria for Word Classes
We began by grouping words more or less on the basis of our instincts about English. We somehow «feel» that brother and car belong to the same class, and that brother and drives belong to different classes. However, in order to conduct an informed study of grammar, we need a much more reliable and more systematic method than this for distinguishing between word classes.
We use a combination of three criteria for determining the word class of a word:
- The meaning of the word
2. The form or `shape’ of the word
3. The position or `environment’ of the word in a sentence
Using this criterion, we generalize about the kind of meanings that words convey. For example, we could group together the words brother and car, as well as David, house, and London, on the basis that they all refer to people, places, or things. In fact, this has traditionally been a popular approach to determining members of the class of nouns. It has also been applied to verbs, by saying that they denote some kind of «action», like cook, drive, eat, run, shout, walk.
This approach has certain merits, since it allows us to determine word classes by replacing words in a sentence with words of «similar» meaning. For instance, in the sentence My son cooks dinner every Sunday, we can replace the verb cooks with other «action» words:
My son cooks dinner every Sunday
My son prepares dinner every Sunday
My son eats dinner every Sunday
My son misses dinner every Sunday
On the basis of this replacement test, we can conclude that all of these words belong to the same class, that of «action» words, or verbs.
However, this approach also has some serious limitations. The definition of a noun as a word denoting a person, place, or thing, is wholly inadequate, since it excludes abstract nouns such as time, imagination, repetition, wisdom, and chance. Similarly, to say that verbs are «action» words excludes a verb like be, as in I want to be happy. What «action» does be refer to here? So although this criterion has a certain validity when applied to some words, we need other, more stringent criteria as well.
The form or «shape» of a word
Some words can be assigned to a word class on the basis of their form or «shape». For example, many nouns have a characteristic -tion ending:
action, condition, contemplation, demonstration, organization, repetition
Similarly, many adjectives end in -able or -ible:
acceptable, credible, miserable, responsible, suitable, terrible
Many words also take what are called INFLECTIONS, that is, regular changes in their form under certain conditions. For example, nouns can take a plural inflection, usually by adding an -s at the end:
car — cars
dinner — dinners
book — books
Verbs also take inflections:
walk — walks — walked — walking
The position or `environment’ of a word in a sentence
This criterion refers to where words typically occur in a sentence, and the kinds of words which typically occur near to them. We can illustrate the use of this criterion using a simple example. Compare the following:
 I cook dinner every Sunday
 The cook is on holiday
In , cook is a verb, but in , it is a noun. We can see that it is a verb in  because it takes the inflections which are typical of verbs:
I cook dinner every Sunday
I cooked dinner last Sunday
I am cooking dinner today
My son cooks dinner every Sunday
And we can see that cook is a noun in  because it takes the plural -s inflection
The cooks are on holiday
If we really need to, we can also apply a replacement test, based on our first criterion, replacing cook in each sentence with «similar» words:
Notice that we can replace verbs with verbs, and nouns with nouns, but we cannot replace verbs with nouns or nouns with verbs:
*I chef dinner every Sunday
*The eat is on holiday
It should be clear from this discussion that there is no one-to-one relation between words and their classes. Cook can be a verb or a noun — it all depends on how the word is used. In fact, many words can belong to more than one word class. Here are some more examples:
She looks very pale (verb)
She’s very proud of her looks (noun)
He drives a fast car (adjective)
He drives very fast on the motorway (adverb)
Turn on the light (noun)
I’m trying to light the fire (verb)
I usually have a light lunch (adjective)
You will see here that each italicised word can belong to more than one word class. However, they only belong to one word class at a time, depending on how they are used. So it is quite wrong to say, for example, «cook is a verb». Instead, we have to say something like «cook is a verb in the sentence I cook dinner every Sunday, but it is a noun in The cook is on holiday«.
Of the three criteria for word classes that we have discussed here, the Internet Grammar will emphasise the second and third — the form of words, and how they are positioned or how they function in sentences.
Open and Closed Word Classes
Some word classes are OPEN, that is, new words can be added to the class as the need arises. The class of nouns, for instance, is potentially infinite, since it is continually being expanded as new scientific discoveries are made, new products are developed, and new ideas are explored. In the late twentieth century, for example, developments in computer technology have given rise to many new nouns:
Internet, website, URL, CD-ROM, email, newsgroup, bitmap, modem, multimedia
New verbs have also been introduced:
download, upload, reboot, right-click, double-click
The adjective and adverb classes can also be expanded by the addition of new words, though less prolifically.
On the other hand, we never invent new prepositions, determiners, or conjunctions. These classes include words like of, the, and but. They are called CLOSED word classes because they are made up of finite sets of words which are never expanded (though their members may change their spelling, for example, over long periods of time). The subclass of pronouns, within the open noun class, is also closed.
Words in an open class are known as open-class items. Words in a closed class are known as closed-class items.
In the pages which follow, we will look in detail at each of the seven major word classes.