last changed in 2010
Notation: `a' - but more often `a<' for pre-adjunct or `>a' for post-adjunct. (2010 abbreviation: a+, +a)
`Adjunct' is the name of one of the basic grammatical functions, and contrasts with `valent' (which covers both subjects and complements), so every dependent is either an adjunct or a valent. Modern adjuncts are roughly equivalent to traditional modifiers or adverbials.
Roughly speaking, a word's valent is a dependent that it 'selects', whereas an adjunct is a dependent that selects it. For example, in (1),
(1) Read this book carefully.
the head word read selects the object this (book) but is selected by carefully. In other words, read needs an object but doesn't need a manner adjunct such as carefully; so after hearing just the word read you're expecting an object, but you're not expecting a manner adjunct.
Putting it another way, any dependency relates two words - the dependent and the parent - and is inherited from (at least) one of them.
This difference can be seen in the following diagram:
According to this diagram, the typical word depends on some other word, but does not necessarily have dependents of its own. This seems correct, but it has the interesting consequence that the typical dependent relation is adjunct, so 'adjunct' and 'dependent' are the same thing.
The following discussion will try to make these rather abstract ideas a little more concrete.
The distinction between adjuncts and complements is very tricky (though subjects are always easy to distinguish from either). The principle is (fairly) clear: complements fill syntactic `slots' provided by the word they depend on, whereas adjuncts don't. For example, in (2) immediately, loudly and at (her trial) are all adjuncts of denied, in contrast with its subject Pat and its complement the (charge).
(2) Pat immediately denied the charge loudly at her trial.
The verb denied has a valency (the list of dependents that the verb expects) which provides slots for a subject and a complement (more precisely, an object); so it is ungrammatical without either of these dependents:
(3) *Immediately denied loudly at her trial.
But the adjuncts are not predicted or required in this way, so they can all be omitted without affecting grammaticality:
(4) Pat denied the charge.
The principle is easy: valents are part of the parent word's valency, adjuncts aren't. What is difficult is to apply this principle to particular cases, which suggests that there may be something fundamentally wrong with it.
The guiding principle when deciding whether some dependent of a word is an adjunct or valent of it is this: you should take it as an adjunct if you can, and only take it as a valent if the facts force you to, because an adjunct analysis is simpler than a valent analysis. An adjunct relationship is justified merely by the characteristics of the adjunct, whereas a valent relationship has to fit the characteristics of the parent as well as those of the valent.
For example, immediately denied is allowed, with immediately as an adjunct of denied, because immediately is allowed to be the adjunct of any verb whose meaning will accept it, as denied does; this is a fact about adverbs, so we do not need to know anything further about denied apart from its meaning. There is no need to show which verbs allow an adverb pre-adjunct and which don't, because they all do.
In contrast, we only know that denied the charge is grammatical because we know that DENY allows an object, and that a verb's object must be a noun (e.g. the pronoun/determine the). If it had been possible to say that a noun such as the (charge) is possible after any verb whose meaning was suitable, the relationship would, by definition, have been `adjunct'; but this is not possible, so we have to settle for the more complex valent analysis.
In this example the answer is clear. The noun after DENY must be a valent because:
Therefore this dependent is obligatory, must follow the verb and must define the 'deny-ee'. None of these facts can be predicted if all we know is that denied is a verb with a certain meaning and the is a noun (with a certain meaning). We also need to know that denied is the kind of verb which takes an object, and how its object contributes to its meaning.
If all examples were like this, life would be simple; but it isn't. In some cases, one or two of these items of information can be predicted from the known facts about the dependent, but one cannot. For example, take the verb PUT as in (5).
(5) Pat put it on the table.
Given what we know about ON, we can predict not only its contribution to the meaning, but also that it should be possible after a verb (e.g. put). What we cannot predict is that put is ungrammatical without it even when the meaning would be clear from the context:
(6) Pat knew it needed to be on the table so she put it *(there).
In other words, the second dependent after PUT is a rather adjunct-like valent. In contrast, we might say that on was a rather valent-like adjunct in (6), if omitting it makes the sentence odd rather than ungrammatical:
(7) Pat kept it on the table.
The same contrast applies, with much the same attendant problems, to the dependents of nouns. These are standardly classified as either valents (complements) or adjuncts, and in the classic example (7) the contrast seems clear:
(8) students of linguistics with long hair
In this case of (linguistics) is a clear complement, while with (long hair) is a clear adjunct. Here are the reasons:
As we might expect, therefore, the same adjunct is possible with any word that has the same meaning as students, such as ones in a context where it means `students':
(9) The students with long hair asked better questions than the ones with short hair.
But when we try to do the same with of linguistics, it fails because ones does not have the right valency:
(10) The students of linguistics asked better questions than the students/!ones of history.
So far so good: but then we find that OF can be used with ones if this refers to pictures, in spite of the peculiar semantic relationship that it expresses there:
(11) The pictures of Pat were better than the ones of Jo.
The question, therefore, is whether the of-phrase after PICTURE is a complement or an adjunct.
In conclusion, the contrast between valents and adjuncts reflects a fundamental and important distinction in the grammar, but needs far more research before we can claim to understand it.
This is an article from the Encyclopedia of Word Grammar and English grammar. If you refer to it, please give the url as "http://tinyurl.com/wg-encyc".