home edit page issue tracker

This page pertains to UD version 2.

Complex Clauses

This section of the syntax overview is devoted to complex clauses, namely:


Complex clauses involving coordination arise when two main clauses or two subordinate clauses at the same level are linked in a coordinate structure, which may or may not involve an overt coordinating conjunction. Coordinate structures are in principle symmetrical, but the first clause is by convention treated as the parent (or “technical head”) of all subsequent coordinated clauses via the u-dep/conj relation. Coordinating conjunctions and punctuation delimiting the conjuncts are attached to the associated conjunct using the u-dep/cc and u-dep/punct relations respectively.

He came home , took a shower and immediately went to bed .
conj(came, took)
conj(came, went)
punct(took, ,-4)
cc(went, and)

Asyndetic coordination occurs when there is no overt coordinating conjunction.

Veni , vidi , vici .
conj(Veni, vidi)
conj(Veni, vici)
punct(vidi, ,-2)
punct(vici, ,-4)

As a special case, the first conjunct may be implicit or part of an earlier sentence.

And then we left .
cc(left, And)

Ellipsis in Clause Coordination

Coordination is often combined with ellipsis, where one or more of the normally obligatory constituents of a clause or omitted because they can be inferred from material in another conjunct.

If the main predicate is elided, an associated aux or cop can be promoted to head of the clause.

Sue likes pasta and Peter does , too .

nsubj(likes-2, Sue-1)
obj(likes-2, pasta-3)
conj(likes-2, does-6)
nsubj(does-6, Peter-5)
advmod(does-6, too-8)
Sue is hungry and Peter is , too .

nsubj(hungry-3, Sue-1)
cop(hungry-3, is-2)
conj(hungry-3, is-6)
nsubj(is-6, Peter-5)
advmod(is-6, too-8)

In more complicated cases where a predicate is elided but no aux or cop is present, promotion can lead to unnatural and confusing relations. For example, in the following sentence, you would be the subject of coffee, suggesting that the second clause contains a nonverbal predication rather than an elided predicate.

I like tea and you coffee .

nsubj(like-2, I-1)
obj(like-2, tea-3)
nsubj(coffee-6, you-5)
conj(like-2, coffee-6)

In such cases, we therefore use the special orphan relation to attach siblings to the promoted element.

I like tea and you coffee .

nsubj(like-2, I-1)
obj(like-2, tea-3)
conj(like-2, you-5)
cc(you-5, and-4)
orphan(you-5, coffee-6)
Mary wants to buy a book and Jenny a CD .

nsubj(wants-2, Mary-1)
xcomp(wants-2, buy-4)
obj(buy-4, book-6)
conj(wants-2, Jenny-8)
orphan(Jenny-8, CD-10)
They had left the company , many for good .

nsubj(left, They)
obj(left, company)
conj(left, many)
orphan(many, good)
Mary wants to buy a book . ROOT And Jenny a CD .

nsubj(wants-2, Mary-1)
xcomp(wants-2, buy-4)
obj(buy-4, book-6)
root(ROOT, Jenny)
orphan(Jenny, CD)

Note that the orphan relation is only used when an ordinary relation would be misleading (for example, when attaching an object to a subject). In particular, the ordinary cc relation should be used for the coordinating conjunction, which attaches to the pseudo-constituent formed through the orphan dependency.


Complex clauses involving subordination arise because a core or non-core dependent is realized as a clausal structure. We distinguish four basic types:

  1. Clausal subjects (u-dep/csubj).
  2. Clausal complements (objects), divided into those with obligatory control (u-dep/xcomp) and those without (u-dep/ccomp).
  3. Adverbial clause modifiers (u-dep/advcl).
  4. Adnominal clause modifiers (u-dep/acl) (with relative clauses as an important subtype in many languages).

In addition, we discuss secondary predicates, which are analyzed as clausal complements or adnominal clause modifiers.

Clausal Subjects

A clausal subject is a clausal syntactic subject of a clause. Its governor may be a verb or a nonverbal predicate. If the governor is in the passive, the subtype csubj:pass can be used.

What she said makes sense
csubj(makes, said)
What she said is interesting
csubj(interesting, said)
What she said was well received
csubj:pass(received, said)

Clausal Complements (Objects)

A clausal complement of a verb or adjective is a dependent clause which is a core argument. That is, it functions like an object of the verb, or adjective.

He says that you like to swim
ccomp(says, like)
mark(like, that)
He says you like to swim
ccomp(says, like)

Such clausal complements may be finite or nonfinite. However, if the subject of the clausal complement is controlled (that is, must be the same as the higher subject or object, with no other possible interpretation), the appropriate relation is xcomp.

The boss said to start digging
ccomp(said, start)
mark(start, to)
xcomp(start, digging)
We started digging
xcomp(started, digging)

The key difference here is that, in the first sentence, who will be starting to do the digging is a question of anaphora (it may be some contextually relevant individual or group, which may or may not include the boss), while in both sentences, the person or persons who are starting to do something are necessarily the same people who are digging (i.e., in the second sentence, the subject of digging can only be we). This is what distinguishes ccomp and xcomp.

The controlled subject of the xcomp can also be an object (obj or iobj) – indeed, it is usually the object when one is present (Visser’s generalization). UD adopts an object with infinitive (or “raising to object”) analysis of such constructions (rather than the “small clause” or “exceptional case marking” analyses that are prominent in many recent strands of generative grammar). So UD uses analyses like the following for cases where there is obligatory control between an object and the subject of a subordinate clause:

Sue wanted Fred to accept the job.
obj(wanted, Fred)
mark(accept, to)
xcomp(wanted, accept)
Sue asked Fred to accept the job.
iobj(asked, Fred)
mark(accept, to)
xcomp(asked, accept)
Please let us know
discourse(let, Please)
obj(let, us)
xcomp(let, know)

(ccomp is no longer used for a copular predicate which is itself a clause: see Predicate Clauses.)

Adverbial Clause Modifiers

An adverbial clause modifier is a clause which modifies a verb or other predicate (adjective, etc.), as a modifier not as a core complement. This includes things such as a temporal clause, consequence, conditional clause, purpose clause, etc. The dependent must be clausal (or else it is an advmod) and the dependent is the main predicate of the clause.

The accident happened as night was falling
advcl(happened, falling)
If you know who did it, you should tell the teacher
advcl(tell, know)
He talked to him in order to secure the account
advcl(talked, secure)
He was upset when I talked to him
advcl(upset, talked)

This relation is also used for optional depictives:

She entered the room sad
advcl(entered, sad)
He painted the model naked
advcl(painted, naked)

Adnominal Clause Modifiers

An adnominal clause modifier is a clause which modifies a nominal.

the issues as he sees them
acl(issues, sees)
Cette affaire à suivre \n This case to follow
acl(affaire, suivre)

A relative clause is a special type of adnominal clause, characterized by finiteness and usually omission of the modified noun in the embedded clause. Some languages use the subtype acl:relcl for relative clauses.

I saw the man you love
acl:relcl(man, love)

Some languages allow finite clausal complements for nouns with a subset of nouns like fact or report. These look roughly like relative clauses, but do not have any omitted role in the dependent clause. This is the class of “content clauses” in Huddleston and Pullum (2002). These are also analyzed as acl.

the fact that nobody cares
acl(fact, cares)

Predicate Clauses

In copula constructions, the predicate may be an entire clause. Because UD does not represent constituent structure, the word that is the predicate of the inner clause does double duty as the head of the outer copula construction. This means that there may be multiple subject relations with the same head—an exception to the usual rule that a word should have at most one nsubj or csubj dependent. The subtype :outer can be used to distinguish the subject that belongs to the outer clause (the innermost nested clause is the “normal” clause; if it has a subject, it does not receive any special designation):

-ROOT- The problem is that this has never been tried .
nsubj:outer(tried, problem)
cop(tried, is)
mark(tried, that)
nsubj:pass(tried, this)
aux(tried, has)
advmod(tried, never)
aux:pass(tried, been)
root(-ROOT-, tried)
The title is Some Like It Hot .
nsubj:outer(Like, title)
cop(Like, is)
nsubj(Like, Some)
obj(Like, It)
xcomp(Like, Hot)

There may be an outer subject with no inner subject:

The important thing is to keep calm .
nsubj:outer(keep, thing)
cop(keep, is)
mark(keep, to)
xcomp(keep, calm)
To hike in the mountains is to experience the best of nature .
csubj:outer(experience, hike)
obl(hike, mountains)
mark(hike, To)
cop(experience, is)
mark(experience, to)
obj(experience, best)

Some languages have zero copula constructions—that is, there is no overt copula, but the nesting is the same, and the outer subject can be distinguished with nsubj:outer or csubj:outer. Here is a Hebrew sentence demonstrating a copular clause nested within another copular clause, i.e. The problem (is) that Kim (is) tired:

ha/DET be'aya/NOUN she/SCONJ Kim/PROPN 'ayefa/ADJ .
det(be'aya, ha)
nsubj:outer('ayefa, be'aya)
mark('ayefa, she)
nsubj('ayefa, Kim)

In principle there could be multiple levels of nesting with multiple :outer subjects (though this is extremely rare in practice):

My memory is that the problem is that Kim will be traveling in March .
nsubj:outer(traveling, memory)
cop(traveling, is-3)
mark(traveling, that-4)
nsubj:outer(traveling, problem)
cop(traveling, is-7)
mark(traveling, that-8)
nsubj(traveling, Kim)

(This was changed from earlier versions of the guidelines, where the outer copula was the head of a ccomp relation.)

Secondary Predicates

A clause can contain a secondary predication or predicative. The most common case is with adjectives, although the same effect can sometimes be achieved with a predicative noun or preposition-marked phrase.

There are two predicates in such sentences, the main predicate and an additional one, such as the cake being beatiful or She being sad.

Huddleston and Pullum (2002) “The Cambridge Grammar of the English Language”, chapter 4 section 5.3, divide predicatives into obligatory and optional predicatives, which can be either depictives or resultatives, and which can appear in an intransitive or transitive clause, giving eight possibilities:

In UD, obligatory predicatives are always treated as an xcomp: The secondary predicate is attached as an xcomp of the main predicate. In most cases, as well as an adjective depictive, you can use a verbal or nominal predicate in the same position (e.g., He looked [an idiot]; This made me [seethe with anger]).

She declared the cake beautiful .
nsubj(declared, She)
obj(declared, cake)
xcomp(declared, beautiful)

In the enhanced representation, there is an additional subject link showing the secondary predication, which is obligatorily a particular role in the higher clause:

She declared the cake beautiful .
nsubj(declared, She)
obj(declared, cake)
xcomp(declared, beautiful)
nsubj(beautiful, cake)

A Czech example:

jmenovat někoho generálem \n to-appoint someone as-a-general
obj(jmenovat, někoho)
xcomp(jmenovat, generálem)

The relation xcomp is used for core arguments of clausal predicates, so it will not be used for some other instances of secondary predication. Optional depictives are analyzed as advcl adjuncts.

For instance, in She entered the room sad we also have a double predication (she entered the room; she was sad). But sad is not a core argument of enter: leaving it out will neither affect grammaticality nor significantly alter the meaning of the verb. On the other hand, leaving out beautiful in She declared the cake beautiful will either render the sentence ungrammatical or lead to a different interpretation of declared.

The result is that in She entered the room sad, sad is considered a modifier (not complement) of the verb, with the relation advcl instead of xcomp. (This was changed from the previous approach which analyzed the secondary predication directly with acl, because the nominal predicand is not always overt, and even when it is, the adjective does not really belong to the same nominal phrase.)

She entered the room sad .
nsubj(entered, She)
det(room, the)
obj(entered, room)
advcl(entered, sad)
punct(entered, .)
Entering the room sad is not recommended .
csubj(recommended, Entering)
det(room, the)
obj(Entering, room)
advcl(Entering, sad)
cop(recommended, is)
advmod(recommended, not)
punct(recommended, .)

Notice that while can be inserted before sad, clearly marking it as a clause.

A Czech example:

Vstoupila do místnosti smutná . \n She-entered to room sad .
advcl(Vstoupila, smutná)
advcl(She-entered, sad)

There is no need to decide whether an example like the following is a depictive or a manner adverbial:

Linda found the money walking our dog .
nsubj(found, Linda)
det(money, the)
obj(found, money)
advcl(found, walking)
det(dog, our)
obj(walking, dog)
punct(found, .)

The optional secondary predication or controlled adjunct subject relation can be represented with an enhanced dependency edge in addition to the advcl relation.

The remaining, most subtle case is optional resultatives. For these, we uniformly use xcomp:

He painted the house blue .
obj(painted, house)
xcomp(painted, blue)

Even though the resultative is optional here, one may argue that it is still a complement (an argument) of the higher verb (he is painting something blue), in a way that is not true of depictives. Such an analysis of optional resultatives as core arguments is adopted for English by Huddleston and Pullum (p. 262). In LFG terms, we would say that the verb has acquired a new subcategorization frame by application of a lexical rule, and that this frame includes an additional xcomp argument. Such an analysis is buttressed by the fact that normally intransitive verbs like to bark can also form similar resultatives by gaining a new subcategorization which adds both a obj and an xcomp, as in the example below.

The dog barked the neighbors awake .
obj(barked, neighbors)
xcomp(barked, awake)