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Using grammar in writing

You have been studying various aspects of the grammar of writings sometimes related to sentences and sometimes related to bigger elements of the text. Throughout this book you have seen examples of different sentence types: you have seen simple, compound and complex sentences. If you look back through some of the texts, you should be able to see that simple sentences (sentences with a single subject and a single verb) are used mainly to introduce a new idea, or to emphasize a point. They are less common in writing than in speech, and they often contain a long, complicated subject, for example:

The long-term goals of agricultural production, industrialization and

population control in China are commendable.

Compound sentences (sentences with two or more clauses joined by and, but or or) are also more common in speech than in writing. Compound sentences join together two closely related ideas in a way which indicates that both are equally important, for example:

Western societies have always admired rainforests but have never understood them.

In writing, most sentences are complex sentences, especially in expository writing. This is because using complex sentences allows the writer to indicate a whole variety of relationships between ideas, and not simply list ideas as if they were unrelated (as would happen with a series of simple sentences) or link them together as if they were equally important (as with compound sentences). Here are just a few examples of complex sentences:

  1. Switzerland, which is a small country with mountains, pine forests and lakes, is famous for winter sports, two of which are skiing and tobogganing.

  2. Although Switzerland is famous for winter sports, visitors go to Switzerland in the summer too.

  3. China has provided significant aid and technical assistance to other countries, both in quantity and quality, despite the fact that its annual income per head is less than £200.

  4. It is surprising that the Arabian conquest of the Middle East took less than a century because the settled populations were large, well institutionalized and supported by the armies of Byzantium and Persia, while the Muslims were far fewer in number and had little in the way of weapons.

One type of complex sentence which is often found in texts designed to convey information is the sentence which contains a relative clause. A relative clause is a clause which contains additional information relating to the main clause of the sentence, for example:


Endocrine glands, which secrete into the blood, are found in various parts of the body.


A level which has the fulcrum between load and effort can be used to compare two masses.

Relative clauses which contain information essential to the meaning or purpose of the sentence are called defining relative clauses. Relative clauses containing information which, although useful, is not essential to the meaning or purpose of the sentence are called non-defining relative clauses. Non-defining relative clauses can be removed from the sentence without changing its meaning or making it ungrammatical, although of course the amount of information will be reduced. The first example on this page is a non-defining relative clause and the second example is a defining relative clause.

Task 6

The following sentences all contain a main clause and a defining relative clause:

  1. find the main clause in each sentence and underline it;

  1. explain to another student why the relative clause cannot be removed from the sentence.

i) Barometers are meteorological instruments which measure atmospheric pressure.

ii) We shall here confine our description to specialized respiratory systems which involve only a part of the body,

iii) An aircraft flying at an altitude of 2,140 metres is subjected to pressures of 80 Kilonewtons per square metre.

iv) Just as remarkable as the evolutionary adaptation of the camel is the adaptation of the group of warm-blooded fish which includes shark, mackerel and tuna. ;

v) Steels which have a carbon content of between 0.5 and 1.3% are known as high carbon steels.

The five sentences in Task 6 illustrate the fact that a defining relative clause limits the meaning of the sentence; without the limitation, the sentence becomes untrue, unclear or ungrammatical (or more than one of these).

In contrast, non-defining relative clauses provide extra information about the subject of the main clause. For example, in the sentence:

Endocrine glands, which secrete into the blood, are found in various parts of the body.

the (non-defining) relative clause tells us what the endocrine glands do, i.e. their function.

Task 7

The following sentences all contain a main clause and a non-defining relative clause. For each sentence:

  1. identify the main clause;

  2. discuss with another student what function the non-defining relative clause has in each sentence.

i) Valves, which are found in most veins, direct the blood flow.

ii) A common northern and eastern plant is the Indian-pipe, which is white while alive but black when dried,

iii) Some epiphytic orchids and other plants have aerial roots, which catch and absorb water from frequent tropical rains.

iv) The dominant aquatic vertebrates are the fishes, which are divided into two subclasses, the bony fishes and the cartilaginous fishes.

v) The kinetic energy of a fluid, due to its motion, is customarily measured with respect to the Earth's surface, which is assumed to have zero velocity.

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