The nature of the information in a sentence

A sentence can be an independent clause, or can be formed by combining clauses, usually with the addition of a linking word or phrase. A clause is a grammatical structure in which several components of meaning are brought together to form a message. The verb is the essential element of any clause.

Simple sentences contain a single clause:

• We knew each other well.
• Have you got the time?
• They drove to Hastings.
• I spoke to her mother.

However, many sentences have more than one clause, so are not simple sentences:

• Sam found his teddy bear
• and climbed back into bed
•  where he pulled the blankets up around his ears,
• closed his heavy eyes,
• and fell asleep.

Clauses can be combined in different ways to make different kinds of sentences: compound, complex, and compound-complex.

Compound Sentences
Compound sentences consist of two or more independent clauses i.e., each is capable of standing on its own and conveying a message. Each has equal status and provides equally important information. These clauses may be linked with connective words or phrases such as: "and", "but", "or", "yet", "so", "and so", "and then", "either...or", "neither...nor", "not only...but also".

She ran to school and threw her bag down in the corridor.

Independent clause Independent clause

* "she" has been omitted due to ellipsis. See ellipsis.

Karl went on camp. but the others stayed at home.	Independent clause Independent clause
You could ring her at the office. or try her on her cell phone.	Independent clause Independent clause

Complex sentences
In complex sentences, there is a clause expressing the main message and another clause (or clauses) which elaborates on the main message in some way. While the main message is independent, the other clause cannot stand on its own: it is dependent.

They smiled as if they meant it.	Independent clause Dependent clause
The plant died because it wasn't watered.	Independent clause Dependent clause
If the container has a hole in it the raspberries will leak all over the bench.	Dependent clause Independent clause

Compound-complex sentences
Compound-complex sentences contain a combination of independent and dependent clauses.

The girls walked out of the shop and laughed loudly* as they headed for the car.

Independent clause Independent clause Dependent clause

* "they" has been omitted due to ellipsis. See ellipsis.

An elderly man was admitted to hospital after suffering a heart attack and falling down his stairs.

Independent clause Dependent clause Dependent clause

Compound, complex, and compound-complex sentences as a source of difficulty in comprehension
Students need to know the meaning of the conjunctions and other linking words if they are to appreciate the relationship between the ideas.

Research indicates that many students don’t fully recognize these relationships and therefore have difficulty in following the meaning of a text. It has been found for example the conditional "if" is understood by only fifty percent of children at age six; that the meaning of "unless" is often not understood well until after the age of nine; and it is generally not until around twelve years of age that many children comprehend the concessive use of "although". (Deriwianka, 2005, p.95)

(b) Adding information to a sentence
Embedded clauses, e.g., adjectival clauses. Adjectival clauses provide extra information about the noun.            

noun Rodents

extra information introduced by settlers

killed the native birds.

The following is an alternative to using an adjectival clause:
Settlers introduced rodents.
These rodents killed the native birds.                          

noun Native trees

extra information that block people’s views or get in the way of property development

are sometimes poisoned.

The following is an alternative to using an adjectival clause:

• Native trees can block people’s views.
• Native trees can get in the way of property development.
• Trees like these are sometimes poisoned.

These types of constructions are often found in simplified text, but students need to gradually develop understanding of how to comprehend and produce sentences with embedded clauses.

Adjectival clauses as a source of difficulty in comprehension
Students need to be able to identify what the adjectival clause is referring to. To do this, they need know:

• How pronouns function (adjectival clauses often begin with a pronoun, e.g., "who", "whose", "which", "that", "where"). These identify what is being referred to.
• Which pronoun is omitted, e.g., "the coat [that] I'm wearing".
• That words other than pronouns are sometimes used, e.g., "introduced by settlers".
• How commas function e.g., in "New Zealanders who don't eat fruit and vegetables will have poor health", the adjectival clause defines which particular New Zealanders are being referred to. But in "New  Zealanders, who don't eat fruit and vegetables, will have poor health", the adjectival clause is referring to New Zealanders in general.

Modals
Modal verbs convey a range of judgments about the likelihood of events. There are nine modal verbs: "can", "could", "may", "might", "will", "would", "shall", "should", and "must".

• She might be there.
• You could get there by lunchtime if you hurry.
• You'll hit the roof.
•  That must have hurt.

To show a high degree of certainty about the likelihood of events, modal verbs of high modality are used. If we feel tentative about something, we use low modality.

High modality	Medium modality	Low modality
must ought to has to	will should can need to	may might could would

(Derewianka, 2005, p.66)

As well as modal verbs, modality can be expressed through choices of nouns, adjectives, and adverbs.

• Modal nouns: "possibility", "probability", "obligation", "necessity", "requirement"
• Modal adjectives: "possible", "probable", "obligatory", "necessary", "required", "determined"
• Modal adverbs: "possibly", "probably", "perhaps", "maybe", "sometimes’, "always’ "definitely", "never", "certainly"

Modals as a source of difficulty in comprehension
Students will need to understand modals in order to use the appropriate degree of probability or obligation, especially when using text types that involve making judgments, e.g., narrative texts, and persuading people, e.g., arguments, advertisements.