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There are two competing notions of the predicate in theories of grammar. The first concerns traditional grammar, which tends to view a predicate as one of two main parts of a sentence, the other part being the subject; the purpose of the predicate is to modify the subject. The second derives from work in predicate calculus (predicate logic, first order logic) and is prominent in modern theories of syntax and grammar. In this approach, the predicate of a sentence corresponds mainly to the main verb and any auxiliaries that accompany the main verb, whereas the arguments of that predicate (e.g. the subject and object noun phrases) are outside the predicate. The competition between these two concepts has generated confusion concerning the use of the term predicate in theories of grammar. This article considers both of these notions.
The predicate in traditional grammar is inspired by propositional logic of antiquity (as opposed to the more modern predicate logic). A predicate is seen as a property that a subject has or is characterized by. A predicate is therefore an expression that can be true of something. Thus, the expression "is moving" is true of those things that are moving. This classical understanding of predicates was adopted more or less directly into Latin and Greek grammars and from there it made its way into English grammars, where it is applied directly to the analysis of sentence structure. It is also the understanding of predicates in English-language dictionaries. The predicate is one of the two main parts of a sentence (the other being the subject, which the predicate modifies). The predicate must contain a verb, and the verb requires, permits, or precludes other sentence elements to complete the predicate. These elements are: objects (direct, indirect, prepositional), predicatives, and adjuncts:
The predicate provides information about the subject, such as what the subject is, what the subject is doing, or what the subject is like. The relation between a subject and its predicate is sometimes called a nexus. A predicative nominal is a noun phrase that functions as the main predicate of a sentence, such as George III is the king of England, the king of England being the predicative nominal. The subject and predicative nominal must be connected by a linking verb, also called a copula. A predicative adjective is an adjective that functions as a predicate, such as Ivano is attractive, attractive being the predicative adjective. The subject and predicative adjective must also be connected by a copula.
This traditional understanding of predicates has a concrete reflex in all phrase structure theories of syntax. These theories divide the generic declarative sentence (S) into a noun phrase (NP) and verb phrase (VP), e.g.
The subject NP is shown in green, and the predicate VP in blue. This concept of sentence structure stands in stark contrast to dependency structure theories of grammar, which place the finite verb (= conjugated verb) as the root of all sentence structure and thus reject this binary NP-VP division.
Most modern theories of syntax and grammar take their inspiration for the theory of predicates from predicate calculus as associated with Gottlob Frege. This understanding sees predicates as relations or functions over arguments. The predicate serves either to assign a property to a single argument or to relate two or more arguments to each other. Sentences consist of predicates and their arguments (and adjuncts) and are thus predicate-argument structures, whereby a given predicate is seen as linking its arguments into a greater structure. This understanding of predicates sometimes renders a predicate and its arguments in the following manner:
Predicates are placed on the left outside of brackets, whereas the predicate's arguments are placed inside the brackets. One acknowledges the valency of predicates, whereby a given predicate can be avalent (not shown), monovalent (laughed in the first sentence), divalent (helped in the second sentence), or trivalent (gave in the third sentence). These types of representations are analogous to formal semantic analyses, where one is concerned with the proper account of scope facts of quantifiers and logical operators. Concerning basic sentence structure however, these representations suggest above all that verbs are predicates and the noun phrases that they appear with are their arguments. On this understanding of the sentence, the binary division of the clause into a subject NP and a predicate VP is hardly possible. Instead, the verb is the predicate, and the noun phrases are its arguments.
Other function words - e.g. auxiliary verbs, certain prepositions, phrasal particles, etc. - are viewed as part of the predicate. The matrix predicates are in bold in the following examples:
Note that not just verbs can be part of the matrix predicate, but also adjectives, nouns, prepositions, etc. The understanding of predicates suggested by these examples sees the main predicate of a clause consisting of at least one verb and a variety of other possible words. The words of the predicate need not form a string nor a constituent, but rather they can be interrupted by their arguments (and/or adjuncts). The approach to predicates illustrated with these sentences is widespread in Europe, particularly in Germany, where the understanding predicates from traditional grammar discussed above seems to hardly exist (for those who know German, see the Wikipedia article in German on the predicate).
The matrix predicate is (again) marked in blue and its two arguments are in green. While the predicate cannot be construed as a constituent in the formal sense, it is a catena. Barring a discontinuity, predicates and their arguments are always catenae in dependency structures.
Some theories of grammar seek to avoid the confusion generated by the competition between the two predicate notions by acknowledging predicators. The term predicate is employed in the traditional sense of the binary division of the clause, whereas the term predicator is used to denote the more modern understanding of matrix predicates. On this approach, the periphrastic verb catenae briefly illustrated in the previous section are predicators. Further illustrations are provided next:
The predicators are in blue. These verb catenae generally contain a main verb and potentially one or more auxiliary verbs. The auxiliary verbs help express functional meaning of aspect and voice. Since the auxiliary verbs contribute functional information only, they do not qualify as separate predicators, but rather each time they form the matrix predicator with the main verb.
The seminal work of Greg Carlson distinguishes between types of predicates. Based on Carlson's work, predicates have been divided into the following sub-classes, which roughly pertain to how a predicate relates to its subject.
A stage-level predicate is true of a temporal stage of its subject. For example, if John is "hungry", then he typically will eat some food, which lasts a certain amount of time, and not his entire lifespan. Stage-level predicates can occur in a wide range of grammatical constructions and are probably the most versatile kind of predicate.
An individual-level predicate is true throughout the existence of an individual. For example, if John is "smart", this is a property that he has, regardless of which particular point in time we consider. Individual-level predicates are more restricted than stage-level ones. Individual-level predicates cannot occur in presentational "there" sentences (a star in front of a sentence indicates that it is odd or ill-formed):
Stage-level predicates allow modification by manner adverbs and other adverbial modifiers. Individual-level predicates do not, e.g.
When an individual-level predicate occurs in past tense, it gives rise to what is called a lifetime effect: The subject must be assumed to be dead or otherwise out of existence.
A kind-level predicate is true of a kind of thing, but cannot be applied to individual members of the kind. An example of this is the predicate are widespread. One cannot meaningfully say of a particular individual John that he is widespread. One may only say this of kinds, as in
Predicates may also be collective or distributive. Collective predicates require their subjects to be somehow plural, while distributive ones do not. An example of a collective predicate is "formed a line". This predicate can only stand in a nexus with a plural subject:
Other examples of collective predicates include meet in the woods, surround the house, gather in the hallway and carry the piano together. Note that the last one (carry the piano together) can be made non-collective by removing the word together. Quantifiers differ with respect to whether or not they can be the subject of a collective predicate. For example, quantifiers formed with all the can, while ones formed with every or each cannot.