Most of the grammatical functions realized by phrases in the sentence fall into two classes: arguments and adjuncts. At Contextors we have put a lot of effort into making our parser distinguish between these two classes, since we believe that the semantic differences between them are useful in designing algorithms for extracting information from sentences; for example: an argument usually designates a participant in the event designated by the verb phrase, whereas an adjunct usually provides other kinds of information. In this article we discuss some of the semantic characteristics of the two classes and mention a structural difference between them.
The arguments of a verb are the phrases that denote the participants in the type of event or situation denoted by the verb. In a sentence like John watched the bird, the verb watched denotes a type of event with two participants: the watcher (identified as John by our sentence) and the object of John’s watching (identified as the bird by our sentence). In a sentence like John loves Mary, John is the person having the emotion of love, and Mary is the person towards whom this emotion is directed. An argument of the verb in the sentence may also denote a content (a proposition); for example: in John thinks that Mary has already left, the embedded clause denotes the content of John’s thought, and in John wants to leave, the embedded to-infinitival denotes the content of John’s desire, namely that John should leave. The arguments of the verb other than the subject are called the complements or internal arguments. Unlike the subject, they are part of the verb phrase.
The argument class consists of several grammatical functions, among them: subject, direct object, indirect object, prepositional complement, etc. As said above, except for the subject, the arguments of the verb are also called complements. A few examples of verbs with different patterns of complementation are given in (1).
In (1a), the verb slept denotes a type of event with only one kind of participant, namely a sleeper, and therefore has only one argument, the subject, which is realized by the noun phrase the child. In (1b) the verb has three arguments: the subject Sue (the “giver”), the indirect object him, which designates the person to whom Sue gave something, and the direct object a book, designating the thing given. In (1c) the to-infinitival clause denotes the content of the farmer’s request to the officials. In (1d) the preposition phrase on the topic denotes the issue in relation to which an agreement was reached. In (1e) the preposition phrases from the village and to the mall respectively denote the starting point (source) and goal of the walk. In (1f) the embedded finite clause denotes a piece of the content of their knowledge.
The term adjunct refers to a family of grammatical functions that includes descriptions of the place and time in which the event denoted by the verb takes place, of the frequency of that event, of the purpose in carrying out the action described by the verb, of the circumstances due to which or notwithstanding which the event took place, etc. Adjuncts are mainly expressed by adverbs, adverb phrases and preposition phrases, but also by noun phrases and non-finite clauses. A few examples of adjuncts that belong to different syntactic categories and realize different grammatical functions are given in (2).
In (2a) the preposition phrase on the lawn specifies the location of the event of their dancing. In (2b) the preposition phrase despite the rain informs us that the rain didn’t prevent them from having a picnic. The adverb quickly and the adverb phrase very convincingly in (2c) and (2d) denote the manner in which the actions described by their respective verbs were performed. The noun phrase tomorrow in (2e) designates the time at which the event of his calling us will take place. The noun phrase a great deal in (2f) is a degree adjunct, and the noun phrase the wrong way in (2g) is a manner adjunct. In (2h), if you join us states a sufficient condition for their happiness. The to- and for-infinitival clauses in (2i) and (2j) provide the goal of the action. Finally, the gerund participial clause speaking honestly in (2k) is a speech-act related adjunct: it describes the speaker’s utterance of the sentence to which the gerund participial clause is adjoined (here the speaker’s utterance of I don’t think you should visit them is described as honest).
While every verb can be modified by adjuncts, many verbs do not take any internal arguments (complements). Whether a given verb takes any internal arguments, and, if so, which, is therefore a lexical property of that verb and is specified in the mental lexicons of speakers and in dictionaries.
The distinction we have made so far between arguments and adjuncts is a purely semantic one: we said that arguments designate the participants in the event, and that adjuncts give other kinds of information about it. In addition, when we look at the examples above we see that the way the meanings of arguments combine with the meaning of the verb is determined by the verb, whereas the way the meanings of adjuncts combine with the meaning of the verb is determined by the adjunct. To explain this point, consider again the sentences in (2a) and (1d), repeated in (3).
In (3a), the preposition phrase on the loan describes the location of the dancing event. This kind of information can be expressed by many other preposition phrases with other prepositions as head, as shown in (4).
In (3b), the preposition phrase on the topic denotes the thing agreed on. As shown in (5), replacing on by other prepositions produces a different kind of meaning altogether.
(5a-b) do not any longer provide information about what was in agreement, but on why and notwithstanding which circumstances the agreement was reached, respectively. These meanings are determined by the prepositions because and despite.
To conclude this section, we give in (6) an example of a sentence where one of the constituents is ambiguous between an argument meaning and an adjunct meaning.
(6) They convinced him to agree on the roof
In (6), the preposition phrase on the roof may be: 1) an argument of the verb agree, in which case it specifies the issue on which they convinced him to agree; 2) an adjunct of the verb convince, in which case it specifies where he was when they convinced him to agree; 3) an adjunct of the verb agree, in which case the sentence means that they convinced him that the roof should be the location where he gives his agreement.
In addition to the semantic difference between arguments and adjuncts, there are several structural differences between them. We will mention one of them here: arguments are usually closer to the verb than adjuncts and less flexible with respect to their position. Consider the examples in (7).
(7a-b) show that there is a preference to placing the argument preposition phrase on the issue closer to the verb than the adjunct preposition phrase despite their insistence. (7c-d) show that it is much easier to place an adjunct preposition phrase at the beginning of the sentence then it is an argument preposition phrase.
The verb is not the only element that may take an argument. Take for example the sentences in (8).
In (8a) the embedded clause is the argument of the adjective certain, providing the content she is certain about. In (8b) the embedded clause designates the content of the claim, and is therefore the argument of the noun claim. Finally, in (8c), the shelf is the argument of the preposition on, which denotes here a spatial relation between the book and the shelf.
In conclusion, the argument-adjunct distinction is based on the semantics of verbs and other argument-taking elements. This distinction has some syntactic consequences, among them the linear order of constituents in the sentence.