1. Relative clauses

2. Relative clauses 1. Used to link two sentences with a common IDEA
In 1937 H. Constant designed a compressor.
This compressor / It ran in 1938 but failed mechanically.

3. Relative clauses
2. The relative pronoun replaces the common element the second time it appears

4. To join sentences using a relative:
Locate the first appearance of the common element.
In 1937, H. Constant designed a compressor.
Add an appropriate relative after the common element
In 1937, H. Constant designed a compressor which...

5. To join sentences using a relative:
3. Add the second sentence MINUS the repeated element
In 1937, H. Constant designed a compressor which ran in 1938 but failed mechanically

6. Choice of relatives Defining Non-defining Antecedent: person
Who / that
Who
Antecedent: object
Which / that
Which

7. Defining vs non-defining
Non-defining clauses are NOT necessary to distinguish who/what you are talking about.
Non-defining clauses go between commas.
No “that” in non-defining clauses
No omission of relative in non-defining clauses.

8. Omission of relatives possible iff
Relative pronoun is who(m), which or that
No comma before the pronoun (therefore, defining clause)
There is a noun/pronoun (subject) between relative and verb.
Molecules absorb energy from the wall (that) they strike

9. Whose
If the repeated element shows possession, use “whose” as a relative adjective.
Whose is always followed by a name
Many high alloy steels are more difficult to cut than mild steel.
Their ingredients retard oxidation.
→Many high alloy steels, whose ingredients retard oxidation, are more difficult to cut than mild steel.