Word and phrase class

classify

This guide will not cover, except in passing, the ground considered in the essential guide to word class so, if you are unsure about any of the following, you should follow that guide first (it opens in a new tab).

Content word classes (nouns, adjectives, adverbs, verbs, interjections)
Functional word classes (pronouns, conjunctions, prepositions, determiners)
Open- vs. closed-class lexemes

That guide sets out the key characteristics of the nine word classes which it considers and exemplifies everything.
This guide is concerned with extending and refining the analysis offered there into areas less often considered.

Language specificity and language differences

You could be forgiven if you believe that word classes are consistent across all languages because that's how many people believe they exist. It is not, however, true.
Even within one well-studied and important language (such as English), there is disagreement about how to classify the lexemes of the language and when it comes to less well-studied and more 'exotic' languages, no consensus at all is discernible.
It is the case, however, that languages which are related, such as the Indo-European ones, do share nearly all the word classes although some are used differently and in some there are no distinctions between certain classes that are distinguished in others (and vice versa).

It is averred by some, often following Chomsky and ideas concerning Universal Grammar, that the basic classes of words and phrases are consistent across all human languages and, therefore, that nouns, verbs, adjectives and adverbs in particular, will be concepts familiar to all speakers of any human languages.
There are those who disagree and they are usually comparative linguists whose concern is to identify and analyse how language differ and how they are similar to each other.
From that school of thought, only the first two categories of words, nouns and verbs, can be said to exist in all languages and other classes either do not exist or are so different from the classes of words in other languages that new categories and quite different analyses are called for.
We shall return to this important area once we have considered the word classes and subclasses that have been identified for the English language.

Word class in English

There are, by the usual estimate, around 170,000 words in English, not including derivatives and rare technical terms, and we need, therefore, to make some sense of the data by a process of classification. That is the study of word class.

On this site and in many other analyses, we generally recognise the following classes of words:

Category	Word class	Examples
Open-class content words	Nouns	house, place, happiness, Mary, Botswana, paper, luggage etc.
	Verbs	go, arrive, take, put, must, be, enjoy, like etc.
	Adjectives	pretty, helpful, blue, astonishing, alive, outside etc.
	Adverbs	happily, soon, frequently, greatly, noisily, so, very, accordingly etc.
Closed-class function words	Conjunctions	and, so, because, but, although, so that etc.
	Pronouns	he, she, it, mine, his, theirs, I, you, we etc.
	Prepositions	in, out, below, in front of, beside, between, underneath etc.
	Determiners	the, an, some, many, each, both, every, those, these etc.
The grey area	Interjections	whoa, wow, gosh, damn, ouch, my my etc.

This will be familiar ground if you have followed the essential guide to the area or the guide to syntax on this site.
However, we will briefly summarise the main features of this classification in order to have some basic terms clear.

The first four categories are considered open-class content word classes to which additions are readily made and which, standing alone, carry a signification which members of the speech community can readily explain.
We can, for example, coin a new adjective whenever we want to express an attribute of something which is new to us or new altogether. So, for example, an adjective such as ferrety could be coined at will to describe something which looks or behaves like a ferret by analogy with catty, doggy, horsey, foxy and more. From that adjective, we can make an adverb and even a new noun such as ferretiness.
Equally, we can invent new nouns and verbs to describe entities and events or states which are new and for which no precise word currently exists. From time to time, such coinages stick in the language and become dictionary entries in their own right. Most don't.
The second four categories are considered members of closed-class, functional words to which additions are very rarely made and which, standing alone, defy clear definition and whose significance is only clear when they function in the syntax of the language.
Although have been attempts to coin new pronouns in particular (see the guide to gender for some examples) most have been unsuccessful.
The final class falls into a grey area because, although the words carry some kind of meaning in context, standing alone they do not and they also do not perform a distinct grammatical function. It is, however, an open-class set of words because new interjections are coined all the time.

Starting from the recognition of the main word classes like this, we can refine our categories, leaving aside the marginal interjections (which can also be further subdivided by the emotions they signal), by putting items into subclasses and end up with something more sophisticated, like this:

Categories:	Functional words (closed classes)			Content words (open classes)
Word class	Sub-categories			Examples
Nouns	count			house, achievement
	mass			happiness, information
	proper			Mary, The Thames
	collective			army, family
	pronouns	personal	subject	we, you, they
			object	us, him. them
			reflexive	ourselves, myself, themselves
			reciprocal	each other, one another
			genitive	ours, mine, yours
		impersonal		someone, anyone, both
Verbs	main	intransitive		go, arrive, rain
		transitive		put, tell, pass
	copular	colourless		be
		pseudo		seem, appear, grow
	auxiliary	modal		must, could, may
		primary		have, be, do, get
Adjectives	stative			pretty, long,
	dynamic			unhelpful, nasty, naughty
	inherent			blue, upright, watery
	non-inherent			great (friend), close (relation)
	denominal			copper, law
	classifying			sports, French
Adverbs	time			soon, then
	manner			happily, noisily
	place			there, northwards
	extent			greatly, hugely
	frequency	definite		monthly, seasonally
		indefinite		frequently, often
	intensifying	downtoners		slightly, partially
		amplifiers		extremely, very
		emphasisers		plainly, simply
	disjuncts			personally, politically
	conjuncts			consequently, additionally
Conjunctions	subordinating			because, although
	coordinating			and, but, or
Pronouns	personal	subject		he, she, we
		object		him, her, them
		reflexive		myself, ourselves, itself
		reciprocal		each other, one another
		genitive		mine, yours, hers
	impersonal			anybody, no-one
Prepositions	temporal			before, until
	spatial			between, in front of
	causal			because of, owing to
	agentive			by
	topical			about, on
	contrastive			like, unlike
	concessive			in spite of, despite
Determiners	article			the, an, a
	demonstrative			those, that
	distributive			each, both, every
	interrogative			who, which, what
	possessive			my, our, your
	quantifying			many, some, much

And, although this is a much fuller description, there are further sub-categories which could be invoked for many of these items.
The other issue here is that we have had to change the background colours of some items and categories because the category of verbs, for example, covers both open-class content words (main verbs) and closed-class functional items (auxiliary and copular verbs).
The category of pronouns is often considered a subsection of nouns (see below) because they act in noun-like ways but they are still functional rather than content lexemes. We have left this class in both positions although that is not very consistent.

There are problems with any categorisation of reality because items have an annoying tendency to slide between classes. For example:

The words this, that, these and those are determiners in:
    Take this glass
    I want that pen
    Try these glasses
    Pass me those bags
but function very differently in:
    Try this
    Take that
    Give him these
    I want those
where they are all pronouns.
Other determiners such as one, each, all, both display the same slipperiness.
(The word that also appears as a subordinating conjunction in, e.g.:
    She told me that she was going out.)
The word outside is given as an example of an adjective which it is in:
This is outside furniture
but in
She went outside
it is an adverb
The word since is
a conjunction in:
    Since she wasn't invited to his party, she didn't invite him to hers
a preposition in
    I haven't seen her since the meeting
and an adverb in
    I saw her this morning but not since.

There are plenty of other examples of this categorical indeterminacy in the guide to gradience (new tab).

A further difficulty lies in the fact that although words may fall quite neatly into major classes, the function they perform, syntactically, grammatically and communicatively may be very variable. There is no doubt, for example, that the word could should be categorised as a verb but it is one of a very different order from verbs such as cook and different again from a verb like be. That distinction has been captured in the second table.

We should remember, therefore, that this is not by any means the only way to categorise the lexemes of the language.
Traditionally, what we have categorised above as determiners, for example, have previous been dealt with as separate categories for possessive adjectives: my, your, her etc.; demonstrative adjectives: this, that, these, those; quantifiers: many, a few, a good deal of, some etc.; articles: a, an, the, Ø (sometimes including some) and so on.
Quirk and Greenbaum (1973:18) also distinguish demonstratives and articles as separate word classes.

Other more recent categorisations, notably that of Huddleston et al (2002:22), follow something broadly similar to what is used here, although the preferred description is lexical category rather than word class, but with significant differences:

The first four content-word categories are parallel.
Pronouns are demoted from a separate category and subsumed as a subset of nouns (because that is how they act).
The category of conjunctions is removed and replaced with two distinct classes:
1. Subordinators: that, for, to, whether, if etc.
2. Coordinators: and, or, but, nor etc.
A new category, determinative, is proposed to include: the, this, that, a(n), some, all, every, each etc.
This is to separate the grammatical function of determination from the lexical category of determinative. So, for example, while the word that in:
that car
is a determinative, the same word functions differently in, e.g.:
it was that close
where it occurs as part of an adjective phrase.
Determinatives considered in this way may only occur as part of a noun phrase whereas the function of determination can be achieved in many ways.
Disjuncts, whether style or attitudinal, and conjuncts, may be considered functional words although they clearly do carry content. We have put conjuncts into the category of functional words because they perform a conjunction role and left disjuncts in the content-word category. That's not a serious issue.

This may seem, and is, a somewhat minor and theoretical distinction but, because word class (or lexical category) is such a fundamental aspect of any understanding of syntax, it is, in reality, quite important.

We shall persist here and in other guides with the 9-part identification of word class that is set out above but that is more from considerations of usability in the classroom and familiarity than theoretical judgements concerning the sustainability of the concepts.

In the essential guide to word class, the relationships and examples are illustrated like this which leaves out a good deal but focuses on the most important areas and subclasses:

summary1

You can get it as a PDF document by clicking here.

Alternative, slightly simpler classifications might look like this:

As we did above, in this arrangement we have included pronouns as a subset of nouns (following Huddleston et al) as well as giving them their own category as function words. Which arrangement you favour is a matter of choice. It would be possible to graft onto that diagram the various sub-categories of most of the classes. We have not done so here in the interests of clarity.
As the outline of a word-class syllabus, the simpler diagrams would serve well.

Other possible word classes

When one steps beyond English, the possible word classes multiply and scholars of some languages have been forced to invent new categories of words because the language they are studying requires it.
This is especially true of what are considered functional words but, as we shall see, not only those.

Here are some possibilities:

clitics
are kinds of affixes which depend on another word phonologically and are bound (i.e., having no separate existence).
Examples are:
In English, n't stands for not and 're for are
In German ge is attached to a past participle form
In Greek possessive determiners are attached to the ends of noun
In Czech many prepositions are clitic forms
and so on
coverbs
are verbs which only occur in cooperation with other verbs. For example, in Chinese languages many verbs occur in chains so
I read it for you
may be roughly translated as
I help you read it
Also in Chinese languages, coverbs, sometimes referred to as preverbs, can express prepositional aspects of verbs and are conjugated as normal verbs.
particles
are often referred to in English as items which are not quite adverbs and not quite prepositions such as the word up in:
Look the word up
In other languages, these are frequent forms so, for example,
In Greek tha signals a future form of any verb
In Chinese languages there are particles to signal verbal aspects, voice and modal forms.
By definition, particles are invariable and show no changes for number, gender or case.
adpositions
encompass prepositions (as most are in English) post-positions (as they are in Japanese and Turkish) and circumpositions, as we find in English (from now on) and in other languages, particularly Pashto and Kurdish but also in Dutch, Chinese, French, Swedish and more.
measure words or classifiers / counters
occur in many Asian languages, including Japanese, Chinese languages, Korean, Assamese, Bengali, Persian and Thai and are items attached to certain nouns without which it is not possible to speak of them. They are akin (but not closely) to partitives in English.
Japanese, for example, has classifying terms for cylindrical objects, animals, bird-like organisms, people, mechanical objects and flat-objects.
Chinese languages also make extensive use of classifiers for, for example, trees, wavy, long things and so on. English uses them rarely although head in head of cattle is an example.

Open and closed-class items

Even this very basic division is not mirrored in all languages.
In Japanese, for example, adjectives are a closed class of words and new ones are formed in a variety of different ways. Pronouns, on the other hand, are members of an open class and new ones can be coined extensively. In some languages, such as Persian, verbs are a closed class and there are only a few hundred of them.

In most Indo-European languages, however, the distinctions between open and closed classes is parallelled and in all languages, it seems, demonstrative determiners and question words constitute closed-class items.

Assigning words to classes

There are three ways we can do this, none foolproof.

Meaning

We can start with what words mean and form our categories accordingly so we can state, for example:

Words that refer to actions are verbs
Words that refer to people or other entities are nouns
Words that refer to the property of something are adjectives
Words which refer to the frequency, time, place or manner of an action are adverbs

This will work as a definition for many words and from a set of rules like that it is possible to classify a list like this:
dig, extremely, go, great, happily, house, Mary, often, potato, read, trivial, yellow
into a classified list like this:

Verbs:	dig, go, read
Nouns:	house, Mary, potato
Adjectives:	great, trivial, yellow
Adverbs:	extremely, happily, often

Unfortunately, however, it does not help us to classify words such as:
exist, loss, installation, openness
and thousands more because such words do not fit the meaning (or semantic) categories. In that list we have:
exist which is a verb that does not represent an action
loss which is a noun that cannot be used to represent an entity
installation which is a noun that refers to an action
openness which is a noun that refers to a property of something or someone
and the list goes on.

Form

If meaning categories don't work, we can try categorising words by their form so we have lists such as:

Nouns take plurals in -s or -es and can take a genitive ending in 's
Adjectives take comparative forms in -er and -est
Verbs take -s on the third person singular and -ed to signal a past tense
Adverbs end in -ly and are formed from adjectives

and that will allow us to categorise, for example:
biggest, coldly, computer’s, corrected, crocodiles, cups, enjoys, exceptionally, fairest, fortunately, goes, hoped, longer, older, Peter's, wilfully
but will not work with many words because

not all adjectives form comparative and superlative forms like this or at all (e.g., fascinating, lost)
some adjectives end in -ly (e.g., likely, motherly)
some adverbs don't end in -ly (e.g., outside, often)
lots of verbs are irregular (e.g., go, went, gone, put, put, put)
some verbs take no -s for the third person singular (e.g., can, must, should)
some adjectives have no comparative or superlative forms (e.g., rural, absent, sunken)
some nouns have irregular plurals or no plurals at all (e.g., information, sheep, mice)

Form is, in other words an inconsistent way to categorise words. It is not unusable, of course, because many words we encounter can be categorised by looking at the form.

Function: the slot test

Here we are on safer ground and it is here that the concepts of syntax and word or phrase categorisation feed off one another. We are considering the possible distribution of items within the syntax of a language.
The way to determine an item's function is to place it in a syntactical environment so, for example, if we are faced with the gaps in these sentences, we can think of them as slots to be filled and then consider whether the syntax of the language will constrain our choices.

She has lots of __________
we can only insert a noun or noun phrase into the gap such a large dogs.
We cannot, for example, insert in, happy, many, do and more.
She can __________
we can only insert a verb phrase and no other category such as dance well. We cannot, for example, insert without, sad, because, radios and more.
I saw the very __________ unicorn
we can only insert an adjective or adjective phrase such as happy. We cannot, for example, insert in front of, extremely, lots, smoke and more.
She walked __________ the road
we can only insert a preposition such as over. We cannot, for example, insert because, yellow, and, carried and more.
They have not __________ enjoyed the food
we can only insert an adverb or adverb phrase such as greatly, often. We cannot, for example, insert beforehand, delicious, some, read and more.
She came __________ I asked her nicely
we can only insert a conjunction such as because. We cannot, for example, insert in, bicycle, however, do and more.
I discovered that __________ student was late
we can only insert a determiner such as a. We cannot, for example, insert back, disconnect, although, perhaps, do and more.
When I dropped __________, the glass broke
we are constrained to insert a pronoun (and in this case, only one pronoun, it) although a noun phrase such as the thing is a possibility. As nouns and pronouns perform identical syntactic functions, however, this is not damaging to the case. We cannot insert, for example, happily, only, before, association and more.

This way of assigning words to word classes, while being the most difficult to apply, is the one that unequivocally works to categorise the lexemes of the language. It is independent of meaning and form.

Phrase classes

We can, of course, extend the analysis of word class to encompass the grammatical and syntactical characteristics of phrases (and clauses to some extent) so while we can now, using the slot test, be able to say that a sentences such as
Birds fly south
can be broken down into Noun + Verb + Adverb
we can also state that:
Those birds have flown to the south
also contains a Noun phrase, a Verb phrase and, if not an adverb, then the next best thing, an adverbial.
The guide to syntax, linked below, explains how the constituents of phrases may be analysed.

The following classification is based on Huddleston et al (2002:23):

phrases

To explain:

Verb phrase: In many analyses, including some on this site, a verb phrase is said only to contain verbs so while:
    must have been being delayed
qualifies as a verb phrase, because it contains only verbs, a phrase such as
    broke open the box very forcefully
is not, per se, a verb phrase because it contains the object noun phrase (the box) and the adverb phrase (very forcefully) as well as the adverb open.
However, for many teaching purposes, conflating other elements into a verb phrase makes sense units clearer.
The only obligatory element of a verb phrase is the verb itself and that must be a main verb rather than a copular or auxiliary verb so, therefore:
    Wait
qualifies as a verb phrase but
    is
    seems
    could
    has
do not.
Noun phrases: may contain a number of elements, like this:
    the old people in the bar
containing a determiner, an adjective, a plural noun and a prepositional phrase.
The phrase itself performs the grammatical functions of a simple noun, however, because it can act as the object or subject of a verb as in:
    She addressed the old people in the bar
or
    The old people in the bar left
You will not be alone if you have noticed that the first example here is slightly ambiguous:
Does it mean that the old people she addressed were the old people in the bar or does it mean that the place she addressed the old people was the bar?
In other words is the structure:
    Subject + Verb + Object noun phrase
or
    Subject + Verb + Object noun phrase + Adverbial prepositional phrase?
The guide to syntax, linked below, explains how we can test for what the constituents of a clause really are and get rid of the ambiguity.
The obligatory element of a noun phrase is the noun itself but the rules for determiners in English sometimes mean that countable singular nouns cannot stand alone without a determiner.
Nouns may be pre- and post-modified in a number of simple and quite complicated ways in English and for more in this area, consult the guide to noun-phrase nominalisation, linked below.
Nominals: also perform the function of nouns but may be formed from a variety of phrases and clauses as in, for example:
    In the house is the best place to study
in which the prepositional phrase acts as the subject of a verb
    Blue and green would be better
in which an adjective phrase has been made the subject and operates as a noun
    Practising her speech helped her a lot
in which a non-finite verb phrase with its object noun phrase acts as the subject of the verb.
There is a little more in the guide to syntax concerning nominals.
Adjective phrases: are an area of some dispute. In some analyses, the phrase which barked at me in
    That's the dog which barked at me
is considered an adjective phrase because it describes the dog. On this site, we stick with calling it a relative pronoun clause.
Adjective phrases may contain a variety of elements and could be:
    very beautiful
made up of an adverb and an adjective
    driven by John
made up of a non-finite verb and a prepositional phrase
    old and angry
made up of two coordinated adjectives and so on.
Adverb phrases: may consist of more than adverbs and can include prepositional phrases as in, e.g.:
badly under the weather
and so on.
Although prepositional phrases are not themselves adverbs, they act to modify verbs so they are adverbial. In fact, such phrases are a more common way to modify verbs than adverbs themselves.
For the distinctions between adverbs proper and adverbials, see the guide to adverbials, linked below.
Prepositional phrases: are also variously analysed. Some consider the noun phrase which is an obligatory element, along with the preposition, to be the object of the preposition and some call it the complement. For teaching purposes, that hardly matters. Examples are:
    over the hill and down the road to the pub
which contains three prepositional phrases, each with its complement / object noun phrase.
Prepositional phrases may contain a non-obligatory modifier in, e.g.:
    clean over the fence
When such words stand alone without a noun phrase as in, e.g.:
    She went out
this site prefers to classify out as an adverb but an alternative analysis is to refer to it as an intransitive preposition. Again, for teaching purposes, this is not something on which to dwell.
Determinative (or determiner) phrases: are rare because most determiners stand alone but they are exemplified by:
    the two
    my many
    our few
etc.
Determiner phrases may contain a head determiner and a pre- and post-determiner as in, for example:
    the last four

Syntactically, in summary, we should consider phrases rather than simple word classes because in most texts, it is phrases rather than single lexemes which perform the grammatical functions we saw above in the section on the slot test.
There is more on phrase structures in the guide to phrases, linked below.

Related guides
the word-class map	for links to guides to the major word classes (or most of them)
essential guide	the guide in the initial plus section to word class
syntax	the guide which considers the interface between words and phrase class and syntax
phrases	for a guide dedicated to the area
constituent analysis	for a guide to how to identify the role of phrases within clauses
adverbials	if you are concerned to know the difference between an adverb and an adverbial
noun modification	for the guide to how nouns may be modified and occur embedded in more complex noun phrases
gradience	the guide which considers how words slide between classes (a phenomenon called categorical indeterminacy)
gender	for a guide which considers attempts to coin new pronouns and determiners
classifiers and partitives	which considers this area in a good deal more detail including the nature of counters and measures
the word class map	from where you can navigate to any of the guides to individual word classes (open and closed)

References:
Huddleston, R and Pullum, GK et al, 2002, The Cambridge Grammar of the English Language, Cambridge: Cambridge University Press
Quirk, R and Greenbaum, S, 1973, A University Grammar of English, Harlow: Longman