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Concourse 2

Complex sentences: the introduction


Note: if you don't know the difference between a subject and an object or your complement from your elbow, it may be wise to follow the guide to the basic components of a sentence which introduces some fundamental concepts.
The other area you might like to cover before this guide is the one on analysing phrase structures.
Both links open in new tabs.
This is called an introduction to complex sentences because there are many ways in which clauses can be connected.  They will not all be covered here but there are links at the end to more specific guides to some of the phenomena exemplified in what follows.


4 Types of sentences

First of all, a little revision is in order.

There are 4 types of sentences represented by the examples below.  Can you identify them?
Click here when you have.

  1. I went to the cinema.
  2. I went to the cinema and I met John.
  3. I went to the cinema because I was bored.
  4. I went to the cinema because I was bored and had nothing better to do.

Note that this classification is one used in so-called traditional grammar.  From other points of view, e.g., functional grammar, all sentences which consist of more than one clause may be defined as complex sentences (Lock, 1996:247).  We retain the distinction here but it is not a necessary one for what follows.

The following examples show that compound and complex sentences are not, of course, confined to two or three clauses:

  1. I went to the cinema and met John but he was bored by the film so he left early.
  2. I went to the cinema because I was bored and had nothing better to do as I'd finished my essay and already sent it in.

In sentence 1. we have a compound of
    went to the cinema
    met John
This is followed by a further independent clause
    he was bored
and a subordinate clause
    so he left early.

In sentence 2., we have the independent clause
    I went to the cinema
followed by a subordinate clause
    because I was bored
and that has a further subordinate clause
    as I'd finished my essay
which is linked to another independent clause
    and already sent it in
The final clause is incomplete because the subject and auxiliary verb (I had) have been ellipted.  We may do this only if they apply to both clauses and only with coordinating conjunctions.

Here's another way to understand it.

Sentence 1 Sentence 2
1 2

An alternative representation of these sentences in which only coordinators are seen as independent elements is:

complex complex

And it is clear that the first sentence contains three coordinated main clauses and one subordinate clause but the second sentence contains one main clause which has two coordinated subordinate clauses, one of which also has two coordinated subordinate clauses.
This is by no means unusual and takes a little bit of unpacking to understand the sense and what see depends on what.


Types of clause

We have distinguished two clause types in the above:

Independent clauses
These are not dependent structurally on other clauses and can stand alone, potentially, at least.
    I went to the cinema
is perfectly comprehensible and the reason need not be given.
This sentence contains two independent clauses, highlighted in green:
     I took the bus to the station  and  I just managed to catch the train
In a compound sentence such as this, the coordinating conjunction is not tied to one or other of the clauses so if we reverse the clauses it remains between them.  There is however, often a semantic rather than syntactical reason for the ordering of the clauses.
We can reverse the clauses in:
    I washed the car and cleaned the house
and make the sentence as:
    I cleaned the house and washed the car
without making any real difference to the sense but we cannot do that with, for example:
    She was tired and went home
without affecting the meaning because:
    She went home and was tired
has a different sense.
The reason is that the conjunction here signals some kind of causal relationship between the events.
When two independent clauses are joined in this way, the subject is often omitted from the second clause so we allow, e.g.:
     I took the bus to the station  and  just managed to catch the train
With coordinated clauses, we can also often ellipt other elements so we can also have:
     I can's see it  or  hear it
in which the auxiliary verb and the subject are ellipted from the second clause.
For more on what can and cannot be ellipted, see the guide to conjunction, linked below.
Dependent clauses
These are also called subordinate clauses for the reason that they are structurally or semantically dependent on other clauses and cannot usually stand alone.  Here's an example with the dependent or subordinate clause highlighted in blue:
     When I came home  I saw that the window was broken.
In spoken language, of course, a dependent clause can stand alone when the independent clause is understood.  For example,
    Why are you so late?
    Because the bus broke down.
In complex sentences the conjunction is tied to the subordinated clause and moves with it when the ordering is reversed.  We can reverse the ordering in
    She came to the pub because she wanted to meet Mary
to have:
    Because she wanted to meet Mary, she came to the pub
but the word because travels with the clause it introduces.
Similarly with our first example we can reverse the clauses and have
    I saw that the window was broken when I came home.
and the subordinating conjunction, when, moves with the subordinate clause.
When we join an independent clause to a dependent clause it is not usually possible to omit the subject so we do not allow, e.g.:
    * When I came home  saw that the window was broken.
Quite frequently, however, for semantic and logical reasons rather than grammatical ones, it is not possible to reverse the clause ordering so, e.g.:
    The train was late, so I missed my connection
cannot sensibly be rendered as
    *So I missed my connection, the train was late

Multicolor Jigsaw

Types of connection: linking and binding

If you are unsure about the difference between the various types of conjunction in English, follow the guide to conjunction on this site linked in the list of related guides at the end.

In traditional grammars conjunction is the name given to clausal connections.  Here, we'll look at things from a slightly different, functional, angle and distinguish between linking and binding.



When two clauses are equal, they can be linked.  Here are some examples with the link highlighted in red.

  1. Stop nagging ; I'll do it tomorrow.
  2. You can stay here with me  or  you can go with your father.
  3. He gave it to me because I wanted it  and  he had no use for it.
  4. While I was walking the dog  and  thinking about the day ahead, I ran into an old friend.

The rule is simple:
For linking to occur, both clauses must be either independent or dependent.

In examples 1 and 2 the clauses are both independent.
In 3 and 4, they are both dependent.  The main clauses in those sentences are He gave it to me and I ran into an old friend respectively.

We can use punctuation, e.g., a semi-colon or dash, to link or we can employ a conjunction.  There are examples of both above.

Sequencing linked clauses

Sometimes, the clauses can be reversed without changing the meaning.  In sentence 3, for example, there is little difference if we say
    He gave it to me because I wanted it  and  he had no use for it
    He gave it to me because he had no use for it  and  I wanted it.
You can see that  and  clearly belongs to neither clause because it remains between them when they are reversed.  That is a defining characteristic of a coordinating conjunction, but not the only one.

At other times ordering is important either because:

  1. There is a logical chronological relationship which is disturbed by moving clauses around.
        I went home and had a long, hot bath.
    is not at all the same as
        I had a long hot bath and went home.
  2. There is an implied causal relationship.
        I was angry and walked out in a huff.
    is not the same as
        I walked out in a huff and was angry.

Subject omission in linked clauses

In linked clauses, we have a frequent example of the omission of the subject.  If the subject of the verbs in both clauses is unchanged, it can be omitted.
    I went out and I caught the bus
means the same as
    I went out and caught the bus.
This cannot happen if we change the subject of the clauses so, in:
    I went out and she stayed at home
we cannot omit the second subject without changing the meaning radically.

Auxiliary omission in linked clauses

By the same token, we can ellipt the auxiliary verb (whether it is modal or primary) providing it applies to both verbs.  In these examples, the subject is also omitted because it applies to both verb phrases.
    I must do my homework and clean the flat
    I had washed the car and put it in the garage



When clauses are unequal, they are connected by binding.

The simplest example is when we have an independent and dependent clause such as:

  1. The room was a mess  because  I'd been too busy to clear up.
  2.  When  I'd finished, it looked a lot better.

In which the main clauses are The room was a mess and it looked a lot better respectively.

Sequencing in bound clauses

Reversing the clauses is possible:

  1.  Because  I'd been too busy to clear up, the room was a mess.
  2. It looked a lot better  when  I'd finished.

However, when clauses are linked in this way the conjunction moves with the clause.  That is to say it is part of it.  That is a defining characteristic of subordinating conjunctions.

Sequencing can be even more flexible with the dependent clause embedded in the independent clause:

  1.  Although   not a good one, the idea was accepted by the board.
  2. The idea,  although  not a good one, was accepted by the board.

We can also have sentences in which a dependent clause has its own dependent clause.  This frequently occurs when causal relationships or relative clauses are used.  For example,

  1. The room was a mess  because  I'd been too busy to clear up  while  I'd been working.
  2. I went to the cinema in the next town  because  it was the only one  which  was showing the film  that  I wanted to see.

Binding without conjunctions

If you have followed the guide to conjunction, you'll be familiar with the range of subordinating (and other) conjunctions used to bind independent and dependent (or subordinate) clauses.  However, there are other ways to bind clauses together.  For example

  1. Had you asked, I would have helped.
  2. By taking a taxi, I managed not to be late.
  3. Arriving at the meeting, I saw that lots of people were going to be late.
  4. The meeting which I attended was not very useful.

In 9, it is word order alone which connects the ideas and the contingent conjunction (if, supposing etc.) has been ellipted.
In 10, the use of the preposition by and a non-finite participle, taking, connects the ideas.
In 11, the non-finite participle alone is enough.
In 12, we have a relative pronoun to connect the clauses.

Subject omission in bound clauses

In linked clauses, we can omit the subject of the second clause if it is the same for both verbs as we saw above.
This is not usually the case with bound clauses even when the subject remains unaltered.  We can have:
    I had worked hard so that I could leave early
but we do not allow:
    *I had worked hard so that could leave early
and we allow:
    She did the work because she needed the money
but not
    *She did the work because needed the money.
With some subordinating conjunctions, however, subject omission is allowable so we may have:
    Although exhausted, she worked on
Nevertheless, including the subject and the verb in both clauses is never wrong and often the only correct alternative.


Catenation, modification, compounding and listing

There are separate guides to catenative (i.e., joined together in a series) verbs and modification on this site, linked in the list of related guides at the end so only brief mention will be made here.  Here's an example:

HYDROUSA intends to set up, demonstrate and optimize innovative on-site nature-based solutions to recover fresh water, nutrients and energy from wastewater, rainwater, groundwater, atmospheric water vapor and seawater to produce marketable products.

There's no doubt that this is a complex sentence but complexity is being achieved in four separate ways:

  1. Pre-and post-modification of noun phrases
    1. on-site nature-based + solutions
    2. energy + from wastewater, rainwater, groundwater, atmospheric water vapor and seawater
    3. marketable + products
  2. Verb listing
    1. set up, demonstrate and optimize
  3. Compounding
    1. adjectives: on-site, nature-based
    2. nouns: wastewater, rainwater, groundwater, seawater
  4. Catenation
    1. the first verb intend is catenated with the three which follow to set up, demonstrate and optimize
    2. those three verbs are all catenated with the infinitive to recover
    3. the verb recover is not catenated with the second infinitive to produce because the to in this case is actually just a shortened form of the complex subordinator in order to

When four different ways of making complexity are used together in this way it becomes quite hard for learners of the language to extract the core meaning.


Problems for learners (and teachers)

Given and new information

There is a tendency in English to end-focus new information, i.e., to place new information after old.  For example,

  1. I finished my essay and went to meet my friends.
  2. When I had finished my essay, I went to meet my friends.
  3. I went to meet my friends when I had finished my essay.

What problems can you see here?  Click when you have an answer.

Conjunct vs. conjunction

What's gone wrong here?  Click when you have an answer.

  1. *I went to the cinema therefore I missed your call.
  2. *I was in London because of this I was able to see the exhibition.
  3. *He came to the meeting additionally so did Mary.

Repeated conjunctions

Some languages (e.g., most Chinese languages) mark the relationships between clauses twice and speakers of those language may produce sentences such as
    Because I was in London so I could meet her.
    Although it was hot but he wore a coat.

Finite and non-finite verb forms

What has gone wrong here?  Click here when you have an answer.

  1. In order that getting to school on time he got up early.
  2. He worked hard so that making a lot of money.
  3. In spite of he worked so hard, he made very little money.
  4. Without I had a satnav I would have been lost.

Click here to take a test on this.

This guide's title includes the word introduction because it has not covered many other aspects of complexity in sentence construction.  The following are all concerned in one way or another with compound or complex sentences.

Related guides:
relative pronoun clauses a guide to how relative pronoun clauses are constructed with considerations of the pronouns we use
conjunction a guide to explain the main sorts of conjunction and distinguish subordinators from coordinators
subordination a guide which extends some of the considerations of binding here
coordination a guide to consider this kind of linking only
adverbials for more on the distinction between a conjunct and a conjunction
conjuncts for the guide which only considers this kind of adverbial
finite and non-finite verb forms for more on this critical distinction
cleft sentences a guide to it-, wh- and other forms of cleft sentences with two verbs
fronting a guide to how moving items to the front of sentences of all kinds can be done for emphasis and the effect on structures which follow
relative adverb clauses a guide to how relative adverbs expressing when, where and how work
indirect questions a guide to reporting or embedding questions
modification an overview of modification with links to specific types
catenative verbs for a guide to how strings of verbs may be used in clauses to attain a level of complexity
negation a guide to a complex and sometimes odd set of phenomena in English included transferred negation and inversion

Lock, G, 1996, Functional English Grammar, Cambridge: Cambridge University Press