Grammatical functions
Subject and object are types of grammatical function. In other words, these terms describe what phrases do in a sentence rather than describing what phrases are in terms of their category (NP, VP and so on). This is a useful dis tinction, because phrases of different categories can perform the same grammatical function, and phrases of the same category can perform different grammatical functions. For example, NP can function either as subject or object:
While the category of a word or a phrase can usually be identified without context, the grammatical function of an expression can only be identified in the context of a particular sentence. This is because the same expression could be a subject in one sentence and an object in another. Compare (21) with (22):
Grammatical functions can be reflected in the word order of a language or by means of a case system (section 14.3.6). Many languages employ a combination of both word order and case.
Subject
The English subject, which is typically an NP but can also be a clause or a PP, can be characterised in terms of a number of morphological and distributional criteria which are summarised in Table 14.2.
We have already seen several examples of the clause-initial position of the English subject. It is worth observing, however, that a subject can be preceded by a topic (23a) or by an adverbial (23b), so that the subject is not always the very first element in the clause.
We have also seen examples of the inversion of subject with auxiliary verbs (section 14.3.3). We return below to case and agreement (section 14.3.6).
Predicate
The term ‘predicate’ refers to the main part of the sentence excluding the verb. Usually, this means the VP, or the verb plus its object(s). The idea that the sentence can be partitioned in this way is widespread in linguistics and reflects the idea that the verb phrase encapsulates the essence of the event that the sentence expresses while the subject is less crucial to defining the nature of the event. Compare the following examples:
In (24a), the predicate ate cakes describes a cake-eating event that happens to involve George. If we change the subject (24b), the sentence still describes a cake-eating event, whereas if we change the object (24c), the sentence describes a different kind of event. It is also striking that idioms occur within the predicate of a sentence:
Observe that the idiomatic interpretation (meaning ‘give up’) is available in (25a) and (25b) regardless of the subject, but if the object is changed from the towel to the flannel the idiomatic interpretation is lost (25c).
Object
This grammatical function divides into two subtypes: direct object and indirect object. Monotransitive verbs like eat, love and see take a single object, which is the direct object. This is bracketed in the examples in (26).
In contrast, ditransitive verbs like give require two objects. Consider example (27).
In this example, Lily is the indirect object and a box of chocolates is the direct object. This type of construction is called a double-object construction. An alternative construction in English reverses the order of the two objects. When this happens, the indirect object (Lily) is expressed by a preposition phrase (to Lily).
Objects are typically NPs but can also be clauses. The English object can be characterised in terms of a number of structural criteria which are summarised in Table 14.3.
Examples (27) and (28) above illustrate the final property in Table 14.3. The second property is illustrated by example (29), which shows that either the direct object a box of chocolates or the indirect object Lily can become the subject of a passive sentence. We return to case below (section 14.3.6).
Predicative complement
The predicative complement is a complement of the verb that is co-referential with or describes either the subject or the object, as in (30a) and (30b) but not (30c):
Unlike objects, predicative complements cannot move to clause-initial position to form a passive sentence. In example (31), been is the past participle of the copula be and was is the past tense form of the passive auxiliary be. The result is ungrammatical:
Adverbial
Finally, as we saw earlier, it is important to distinguish the term ‘adverb’ from the term ‘adverbial’. While ‘adverb’ refers to a word class (for example, suddenly, soon, fortunately), ‘adverbial’ refers to a grammatical function that can be performed by various categories in addition to the adverb, as illustrated by the examples in (32).
For reasons that we will not pursue here, the expression humming a happy tune in (32c) is described as an embedded adverbial clause, even though it lacks a subject.
As these examples illustrate, adverbials are the ‘optional’ parts of sentence that modify the clause at some level and can be added or deleted without making the sentence ungrammatical. Adverbials typically express information about when, where or how something happened. It is difficult to pin down a set of structural criteria that characterise adverbials because they display considerable flexibility in terms of position. However, unlike the other grammatical functions, adverbials can be stacked (that is, can occur recursively):
