English — Reduced relative clauses
A relative clause can be shortened to a participle phrase by dropping the relative pronoun and the verb be: the man waiting outside (= who is waiting), the letter written yesterday (= which was written).
How it works
Use the -ing (present) participle when the full clause is active: the people living next door replaces the people who live next door. Use the -ed / third form (past) participle when the full clause is passive: the books sold out replaces the books that were sold out.
Examples
| Full clause | Reduced (participle) | Voice |
|---|---|---|
| the man who is waiting outside | the man waiting outside | active (-ing) |
| the people who live next door | the people living next door | active (-ing) |
| the girl who was sitting in the corner | the girl sitting in the corner | active (-ing) |
| the letter which was written yesterday | the letter written yesterday | passive (-ed) |
| the books that were sold out | the books sold out | passive (-ed) |
| any decision that is made today | any decision made today | passive (-ed) |
Good to know
You can only reduce when the relative pronoun is the subject of its clause. In the man I saw the pronoun is the object, so no reduction is possible. Also, an -ing participle keeps a continuous/ongoing sense: the man waiting outside means he is waiting now, not that he waits every day.