relative clauses:
The relative pronoun: that/which(things), who/whom(people),whose(usually people). In speaking, that can be used for people but not in formal written English.
restrictive and non restrictive clauses:
Restrictive: weeds that float to the surface should be removed before they decay. (only those that float to the surface)
Nonrestrictive: my car, which is very large, uses too much gasoline.
optional relative clause reduction: removing relative pronoun +verb be + other auxiliary.
Before relative clauses in the passive voice: this is the z value which was obtained from the table areas under the normal curve. Or. This is the z value obtained from the table area under the normal curve.
Before prepositional phrases: the beaker that Is on the counter contains a solution. Or. The beaker on the counter contains a solution.
Before progressive ( continuous) verb structure: the girl who is running down the street might be in trouble. Or. The girl running down the street might be in trouble.
Mr. Jackson, who is a professor, is travelling in the Mideast this year.
Mr. Jackson, a professor, is travelling in the Mideast this year.
other uses of that.
Optional that:
That is optional after –say, tell, think, believe.
John said that he was leaving next week. Or. John said he was leaving next week.
Obligatory that: after the following verbs- mention, declare, report, state.
The mayor declared that on june the first he would announce the results of the search. Mentioned that/ report that/state that.
That clause: it is well known that many residents of the third world country are dying. Or. That many residents of third world countries is dying is well known. That john would do such a thing surprises me.