Pro-drop and ‘dummy’ subjects

A further difficulty for our subject+ predicate definition is the fact that many languages allow sentences not to have a specified subject. This phenomenon is known as pro-drop, and is particularly common in the Romance languages:

It might be argued that the ‘subject’ in these examples is understood, and can in fact be deduced from the personal verb ending.

In non-pro-drop languages, some specified subjects have no obvious referent. What, precisely, is raining in it is raining, for example, and what does ‘it’ refer to in it is clear that we need a new plan? Likewise there in There is a lot of confusion has no referent and serves only to satisfy a requirement that English verbs have a specified subject. Subjects like these, which have a purely grammatical role, are generally known as dummy subjects.

Using a term borrowed from chemistry, syntacticians sometimes refer to the valency of a predicator, meaning the number of arguments associated with the predicate that it realizes. Thus a one-place predicate has a single argument (e.g. the verb exist in (1) above), a two-place predicate (e.g. Sentence 2) has two and a three-place predicate (e.g. Sentence 3) has three.

These arguments are said to be expressed by complements in the sentence, but note that terminology here is inconsistent, with some syntacticians viewing all constituents expressing a grammatical argument as complements, while others exclude subjects from this definition.

In the above examples, the predicator is a finite verb (i.e. one marked for tense), but prepositions, adjectives or nouns may also realize one or two-place predicates. The predicators in the following examples are on, proud and friend respectively.

A requirement of English is that where the predicator is not a finite verb, the sentence requires the appropriate form of the verb to be for it to be grammatical: to be in this context is known as a copula, or linking verb. But not all languages have a copula requirement, as the following examples from Russian, which has neither articles nor a verb to be in the present tense, demonstrate:

1 on inzhenjer (lit. he engineer) ‘He is an engineer.’

2 ona krasiva (lit. she beautiful) ‘She is beautiful.’

3 ja na zavodje (lit. I on factory) ‘I’m at the factory.’