Syntactic theories typically distinguish 2 types of word or phrase accompanying verbs:
- arguments are accompaniments that can be present if the verb permits them to be present (‘licences’ them). Some arguments of some verbs are mandatory but others are optional.
- adjuncts are optional accompaniments that can be present without needing permission from that particular verb. Adjuncts are always optional and in principle there is no limit on the number of adjuncts.
Which arguments a verb licences depends on the verb. For example, consider the verbs devour and dine:
- for devour, a subject and object may both be present, so devour has 2 arguments (example 1).
(1) Jane devoured her meal. - for dine, a subject must be present but the object must not be present, so dine has one single argument (example 2).
(2) Jane dined.
Syntactically, the verbs devour and dine differ only in the number and nature of their arguments. These verbs’ meanings are also similar—though there is a slight difference in connotations because devour suggests ravenous behaviour whereas dine suggests refined behaviour.
Borrowing a metaphor from chemistry, the number and type of arguments licensed by a verb is sometimes called the verb’s valency. Depending on whether it licences 1, 2 or 3 arguments, a verb is called monovalent, bivalent or trivalent.
Adjuncts
It is possible to include adjuncts in examples 1 and 2 to give more detail, for example to clarify the location, time, manner of performance or other circumstances (examples 1a and 2a).
(1a) Jane devoured her meal in the kitchen with her friends at 7 o’clock using a knife and fork.
This sentence has 4 adjuncts: (1) in the kitchen; (2) with her friends; (3) at 7 o’clock; (4) using a knife and fork.
(2a) Jane dined in the kitchen with her friends at 7 o’clock using a knife and fork.
This has the same 4 adjuncts as example 1a.
When it is hard to distinguish arguments from adjuncts
In 3 common cases, it may be difficult to distinguish arguments from adjuncts:
- when an argument is optional;
- when an argument is implied and not stated explicitly;
- when a verb has an apparently unnecessary ‘cognate object’.
Optional arguments
Devour always has exactly 2 arguments and dine always has exactly 1 argument. Some verbs have different numbers (and perhaps types) of arguments at different times. For example, sometimes, the verb eat is accompanied (like devour) by both its subject and object (example 3), but at other times it is accompanied (like dine) by its subject alone (example 4).
(3) Jane ate her meal.
(4) Jane ate.
Different theories would analyse examples 3 and 4 in different ways. For example:
- some theories would analyse eat as having one mandatory argument (the subject) and one optional argument (the object).
- other theories would analyse eat as appearing in 2 different constructions: one construction requiring 2 arguments (both mandatory) and a different construction with only one argument.
Implicit arguments
In some instances, although a verb often requires arguments, one or more of the arguments is not always present explicitly. For example:
- some languages do not routinely express a sentence’s subject if the context makes it clear what the subject is. (Linguists often call this phenomenon ‘pro-drop’.)
- some languages do not express a sentence’s object if the object is clear from the context. (‘object drop’).
Some theories regard ‘dropped’ arguments as present but unpronounced (implicit).
Cognate objects
Some verbs appear readily in 2 different constructions:
- an intransitive construction (example 5); or
- a transitive construction involving a ‘cognate object’: an object formed from the same root as the verb (example 6).
(5) Jane slept.
(6) Jane slept an undisturbed sleep.
A common reason for including a cognate object is to include a modifier, such as undisturbed in example 6. (It may sometimes be possible to introduce a modifier conveying a similar—though not always identical—meaning, eg Jane slept without disturbance).
What can be an argument or adjunct?
Arguments are typically nouns or noun phrases, but are sometimes prepositional phrases.
Adjuncts are typically nouns (or noun phrases), prepositional phrases, adverbs or adverbial phrases.
More about arguments and adjuncts
I have kept this post at a very high level. The exact definition of arguments and adjuncts of arguments and adjuncts—and the description of the structures they appear in—depend heavily on the syntactic theory adopted for analysis.
In many syntactic theories, a verb’s arguments are its complement(s) and/or specifiers. On the other hand, a verb’s adjuncts are not complements of the verb; depending on the theory, they may or may not be a type of specifier. Heads, complements, specifiers and adjuncts – Language Miscellany