1. Lesson 11 (Nov. 24) Relative Clauses

2. First example: – Recall: one simple sentence can only contain one verb. – Here is a pair of simple sentences, one passive and the other active: An object is left in the sun. It becomes hot. – Which is the main piece of information? – The above can be rephrased in one “compound sentence”: An object which is left in the sun becomes hot. which is left in the sun Relative clause

3. Relative Clauses Another example:  Wires are insulated with a plastic covering.  They are used to conduct electricity.  Wires which are insulated with a plastic covering are used to conduct electricity.  What if we exchange the main clause with the relative clause?  Wires which are used to conduct electricity are insulated with a plastic covering. The emphasis is changed!

4. Relative Clauses Yet another example:  A plane is already in service.  It can carry 600 passengers.  A plane which can carry 600 passengers is already in service.  A plane which is already in service can carry 600 passengers. The main clause is what the sentence emphasizes The relative clause provides more information

5. Relative Clauses The most important points about relative clauses are:  Every written English sentence must have a main clause (with only one finite verb).  A relative clause is never a main clause.  Relative clauses begin with a wh- word: which is the most common; who is reserved for people. Relative clauses are used to avoid writing a series of very short simple sentences.  A plane which can carry 600 passengers is already in service.

6. Relative Clauses Very often (but not always), – the main clause describes the result or the principle, – the relative clause describes the conditions under which the result can be obtained.  An object is left in the sun.  Condition  The object becomes hot.  Result  An object which is left in the sun becomes hot.  A matrix has distinct eigenvalues.  Condition  The matrix can be diagonalized.  Result  A matrix which has distinct eigenvalues can be diagonalized.

7. Relative Clauses Both the main and the relative clauses can be either passive or active:  An object which is left in the sun becomes hot.  A matrix which has distinct eigenvalues can be diagonalized. passive active passive active

8. Workshop: Passive Relative Clauses An object is left in the sun. It becomes hot. An object which is left in the sun becomes hot. A bottle is dropped on a stone floor. It usually breaks into pieces. A bottle which is dropped on a stone floor usually breaks into pieces. A balloon is filled with a gas lighter than air. It rises off the ground. A balloon which is filled with a gas lighter than air rises off the ground. A disease is caused by a virus. It is often difficult to cure. A diseases which is caused by a virus is often difficult to cure. Paper is made from alfalfa. It is expensive. Paper which is made from alfalfa is expensive.

9. Placement of the Relative Clause In the previous examples, the relative clauses follow the subject nouns of the main clauses: – An object which is left in the sun becomes hot. – A diseases which is caused by a virus is often difficult to cure. What is the difference between these two sentences? – what does the word which correspond to?  This paper which is made from alfalfa is expensive.  This paper is made from alfalfa. This paper is expensive.  This paper is made from alfalfa which is expensive.  This paper is made from alfalfa. Alfalfa is expensive. – Here, which follows the object noun (alfalfa) of the main clause. subjects

10. Workshop: Placement of Relative Clauses  This water is taken from the river.  The river is polluted by industrial wastes.  This water is taken from the river which is polluted by industrial wastes.  The antenna is designed for a high bandwidth.  This high bandwidth is sufficient for digital voice transmission.  The antenna is designed for a high bandwidth which is sufficient for digital voice transmission.  These roads are surfaced with tarmac.  The tarmac allows higher speeds than stones.  These roads are surfaced with tarmac which allows higher speed than stones. { Main clause } …. object noun which … { relative clause }

11. Prepositional Relative Clauses  This water is taken from the river.  main clause  The river is polluted.  This water is taken from the river which is polluted.  This water is taken from the river.  The river is polluted.  main clause  The river from which this water is taken is polluted. The relative clause above begins with the preposition from. This preposition + wh-word structure presents difficulties to many learners. See how to construct the sentence step by step: 1.This water is taken from the river. The river is polluted. 2.The river (this water is taken from the river) is polluted. 3.The river which this water is taken from is polluted. 4.The river from which this water is taken is polluted.

12. Workshop: Prepositional Relative Clauses  The antenna is designed for a high bandwidth.  This high bandwidth is sufficient for digital voice transmission.  The high bandwidth for which the antenna is designed is sufficient for digital voice transmission.  These roads are surfaced with tarmac.  The tarmac allows higher speeds than stones.  The tarmac with which these roads are surfaced allows higher speed than stones.  A rectifier is an electronic device.  Current is restricted to one direction by a rectifier.  A rectifier by which current is restricted to one direction is an electronic device.

13. Different Ways of Saying the Same Thing  A rectifier is an electronic device.  Current is restricted to one direction by a rectifier. A rectifier by which current is restricted to one direction is an electronic device.  A rectifier is an electronic device by which current is restricted to one direction. The main clause is broken into two pieces which are too far apart. Instead, let which refer to electronic device.