A Typology of Word Categories(23) Words
thematic categories functional categories
V N A P I D Deg C
We will introduce these categories individually in the following sections.3.1 Categorial features
Before we start to look at the properties of individual categories, we will make the
typology of categories described in (23) a little more systematic. One might wonder
why there are these categories and why their division is so regular: four thematic
categories and four functional ones. Moreover, we may have the feeling that the
categories given in (23) are not completely unrelated to each other. For example, it is
often felt that nouns and verbs are somehow opposites of each other or that adjectives
have some things in common with nouns and other things in common with verbs. Even
across the thematic/functional divide, we may see similarities. For example, words like
the, these and some are determiners and these seem more related to nouns, which they
usually accompany, than to verbs. Modal auxiliary verbs, such as may, can and must,
which as we will see are classified as belonging to the inflections, are obviously more
closely related to verbs than nouns.
But how can we explain these perceived relationships? It is certain that if we define
word categories in individual terms, say by just listing possible categories, then any
explanation of the categories themselves or their relationships will be impossible. An
analogy might serve to make the point clearer. Suppose that biologists had never
thought of categorising living things into taxonomic groups and instead simply
identified individual sub-species such as ladybirds, field mice, pythons, etc. From this
perspective it would be impossible to answer questions such as why do ladybirds and
bluebottles both have six legs and wings? At best, biologists would only be able to
claim that this was an accidental chance happening. Once there is a taxonomic system,
such questions are easily answered: ladybirds and bluebottles are both insects and all
insects have six legs and wings. The same is true for word categories. If we merely
identify categories such as nouns, verbs and determiners, we cannot explain
relationships between the categories.
One way to impose a system on elements is to use a set of features to distinguish
between them. Each category can then be defined in terms of a unique collection of
these features, but they may share some of the features with other categories,
accounting for similarities between them. In linguistics, binary features, i.e. those
which can be valued in one of two ways (plus or minus), have been found useful for
producing systems of categorisation. For example, we might propose a feature [±F]
(‘F’ to indicate functional) to distinguish between the thematic and functional
categories. All thematic categories would possess the [–F] feature and all functional
categories would possess the [+F] feature. In this way we can immediately distinguish
between the two groups and account for why certain categories are similar to others in
terms of which feature they possess.