Sentence types: simple, compound, complex

This unit further explains simple sentences, compound sentences and complex sentences, which were introduced in the unit 'Clauses: main and subordinate'. Simple sentences contain one clause, while compound and complex sentences contain more than one clause.

National Curriculum note: The National Curriculum now refers to sentences that contain one clause as single-clause sentences, and those that contain more than one clause as multi-clause sentences.

Simple Sentences

A simple sentence is a main clause which:

• has no subordinate clauses inside it, and
• functions as a sentence in its own right.

A simple sentence is only ‘simple’ in terms of how it is made up of clauses. It is not always very short or very simple in other ways. The sentences below are all classed as simple sentences. They vary in length, and in how many phrases they contain. However, each contains only one verb phrase, which is highlighted.

• Everybody hesitated.
• The firm has launched a full investigation.
• This evening French police were out in force at key points around the city.
• In our property development and investment business overseas, Grosvenor International employs some eighty-five people, with offices in Vancouver, San Francisco, Washington, Honolulu and Sydney.

As a simple sentence contains only one verb phrase, this means it expresses just one situation (event or state). This is often useful, and we can add some detail in the other phrases we include. However, sometimes we need to express more than one situation in a single sentence and relate these situations to each other. Using compound and complex sentences allows us to do this. Let’s see how.

Compound Sentences

You may recall that a compound sentence is a sentence with two or more main clauses, usually joined by a coordinating conjunction like and, but or or. Let’s have a look at some examples and think about how this type of sentence can be useful.

In the following example, the speaker has chosen to use a compound sentence instead of two simple sentences:

• actual example: There are thousands here today and the atmosphere is electric.
• compare: There are thousands here today. The atmosphere is electric.

By linking the clauses with and, the speaker indicates some kind of link between them. The conjunction and does not tell us specifically what kind of link. But we can work out that these are two related facts – the thousands of people probably help to create the electric atmosphere.

What about the following example? What kind of link between clauses does and make here?

• And my dad had gone out and he’d bought vests and nappies and he’d washed them all and aired them all.

In this case and links together a sequence of events – a set of related purposeful actions carried out by the speaker’s father.

What about this example with but?

• actual example: ‘Jethro’s a good lad but he’s keeping bad company.’
• compare: ‘Jethro’s a good lad. He’s keeping bad company.’

The conjunction but here relates two comments about Jethro and contrasts them. On the one hand, his character is described as good; on the other hand, the company he keeps is said to be bad.

Here is an example with or:

• actual example: I may be staying around to the end of the week or I may go back tomorrow.
• compare: I may be staying around to the end of the week. I may go back tomorrow.

Here or links together two possible alternatives (and suggests that these are the only two).

Here is an example where many clauses are linked together in a compound sentence:

• actual example: Money supply growth is weak, the housing market is flat, unemployment is rising rapidly and wage settlements are falling.
• compare: Money supply growth is weak. The housing market is flat. Unemployment is rising rapidly. Wage settlements are falling.

Here, the clauses in the actual example are grouped together by punctuation (commas instead of full stops) and by an and before the final clause. This is a way to link together a list of points, instead of just stating them one after another. They are all points describing economic conditions, so it makes sense to link them.

Linking clauses together with coordinating conjunctions is a bit like chaining them together. This works well for a list of points or events. However, it is not very flexible. We’ll look next at complex sentences, which provide more possibilities.

Complex Sentences

In a complex sentence, a subordinate clause functions as part of a main clause. This type of sentence is very flexible, allowing us to make a wide range of different links between situations or ideas.

What kinds of meanings do you think are added by the highlighted subordinate clauses in these examples?

• Warm ocean water heated by the Sun cannot rise because it is already at the top of the ocean.
• If it’s a really nice day we could walk.
• I put Emily back in her own bed after she’d fallen asleep.

The subordinate clause adds a different type of meaning in each example: a reason (because ...), a condition (if ...), a time (after ...).

In each of these examples, the subordinate clause functions as an Adverbial. In terms of grammar, the Adverbials are not essential to complete the sentences (i.e. if we leave these clauses out we still have complete sentences), but they add circumstantial meaning.

There are many other kinds of meanings that can be added with different subordinating conjunctions like although, unless and whereas.

Complex sentences are often used to report the content of what someone says or thinks:

• The Foreign Secretary said that the Gulf War had exposed deep divisions and differences between member states on key issues.
• But afterwards she thought her experience had been worth it.
• I was only wondering how it works.

In these examples the subordinate clauses (highlighted) function as Direct Object: they come right after the verb phrases of the main clauses and are very important in completing the sentence structure. They tell us what the Foreign Secretary said; what 'she' thought, and what 'I' was wondering.

Note: We have focused here on complex sentences with finite subordinate clauses (i.e clauses with tensed verbs). In other resources we will also look at nonfinite subordinate clauses (i.e. those without tensed verbs), as in Coming down the stairs, she fell and twisted her ankle.