Sentence types

In writing courses and in sentence grammar, we often distinguish the following types of clauses, which then form different types of sentences.

type	definition	discourse function
Main or independent clauses	subject + verb (+object / predicate) - SVO Can exist by itself as a sentence	Foregrounds a main idea
Subordinate (dependent) clauses	sub. conjunction + SVO Cannot exist by itself as a sentence	Backgrounds information, making it secondary to that of the main clause

1 Basic clause-sentence types

Subordinate clauses that background information mainly include what are sometimes called adverbial subordinate clause. There are other types of subordinate clauses: relative clauses, for modifying nouns, and complement clauses for expressing complex ideas by embedding one clause into a higher clause as a subject or object of the higher clause (e.g., I know what you are thinking, I know that you are planning something).

These types of clauses can form the following sentence types.

type	definition	example	function
Simple	one main clause	The iguana ate the rodent.	Foregrounds activities and ideas
Compound or coordinate	two main clauses joined by a coordinating conjunction	The iguana at the rodent and the cheetah chases the zebra.	Foregrounds two clauses equally in sequence
Complex	main clause + subordinate clause	Zebras hate cheetahs because they always try to chase and eat them.	Backgrounds one idea to a main idea
Compound-complex	two main clauses + subordinate clause (or main clause + two subordinate clauses)	Some mammals hibernate in winter, but others simply adapt to cold weather, because they have evolved to adapt to and to exploit their niches differently.	Juxtaposes two foregrounded ideas with a backgrounded idea, e.g., for explanation

A subordinate clause might go before a main clause to present secondary information leading up to the content of the main clause; or a subordinate clause could come after the main clause, to provide further explanation, evidence or support for the idea of the main clause.

• Because they always try to chase and eat zebras, zebras hate cheetahs
• Zebras hate cheetahs because they always try to chase and eat the zebras.

There are also non-finite clauses or phrases, such as participle phrases, and verbless clauses with be omitted (for modification).

• Having finished all my research writing, I decided to take a vacation.
• He talked about the different patients he was treating, many of them mentally ill.

2 Canonical verses non-canonical sentences

Canonical sentences are basic SVO sentences for normal foreground-background flow. Other types of sentences are used in academic writing, narrative writing, and informal types of writing.

	type	definition	example	function
Passive	The object becomes the subject; the agent, cause or performer of an action may optionally be expressed with by + noun	A mixture of 4% acetic acid was prepared, enhanced with ground resins and aromatic compounds, and added to the salad; it was referred to as balsamic.	Focus or attention is on the subject, and what happens to it, rather than what it does
Inversion	An adjective, adverbial, or prepositional phrase moves to subject position, and the subject comes after the verb. INV. + VSO	The farmer entered the chicken coop, not suspecting the chickens would revolt against him. As he started to prepare their feed pellets, in the corner there appeared a large angry rooster with a knife, ready for hand-to-hand combat.	Makes a transition from one topic scene or topic to a related topic – a smooth topic shift or scene shift

The following sentence types are informal, colloquial, or conversational.

type	definition	example	function
Cleft	It’s the X that...	A: The program comes in 32-bit and 64-bit versions. Would you like the 32-bit? B: It’s the 64-bit version that I need.	emphasis and contrast, between alternatives
Wh-cleft (pseudo-cleft)	What [clause] is...	A: We only have the 32-bit in stock. B: What I need is the 64-bit version.	emphasis and contrast, between alternatives
Preposing (preposed object), topicalization	object or phrase moved to sentence initial position; VSO sentence	She prepared several gifts for the committee members. One of these gifts was a toy phaser for the Trek fan; another was a little Tardis for the Dr Who fan. ... <quotation> A: Can I get a muffin? B: We’re out of muffins. A bagel I can give you. Or an omelette. A: Okay. B: So, a bagel you want? </quotation> ... <quotation> I think he was Russian. No, Ukranian he was. </quotation>	highlighting or emphasis (often said with emphatic intonation); sometimes used for repairs and echo questions.
Left dislocation	Object moved to subject position, with corresponding pronoun in the predicate	Bronchitis is manageable. But pneumonia, you have to go to the hospital for that.	Amplifies a new item or topic in the discourse.
Extraposition (extraposed subject)	Complement clause moved out of subject position, with a dummy pronoun left behind	That I overslept was regrettable. → It was regrettable that I overslept.	Avoiding complex complement clause in subject position, which is harder for listeners to process
Like-cleft	It’s like...	I’ve tried the experiment three different ways. It’s like, I don’t know what to do.	Highlights or emphasizes the following clause, and can also soften or qualify it (some like as if)