Reduced Relative Clauses in English — Active & Passive Participles

A reduced relative clause is a relative clause that has been shortened by removing the relative pronoun (who/which/that) and the auxiliary verb (is/was/are/were), leaving only a participial phrase. Full: The car that is parked outside belongs to my neighbour. Reduced: The car parked outside belongs to my neighbour. The meaning is the same but the sentence is more concise and formal.

Use -ing when the relative clause is active (the subject does the action): The boy who is playing football = the boy playing football. Use the past participle when the relative clause is passive (the subject receives the action): The car that was stolen = the car stolen. The key question is: is the noun doing the action (-ing) or receiving it (past participle)?

No. A relative clause can only be reduced when the relative pronoun is the subject of the relative clause. Full: The teacher who teaches us is kind (who = subject → can reduce: the teacher teaching us). Cannot reduce: The book (that) I read last night was excellent (that = object, not subject → cannot reduce). The object relative clause can still drop 'that', but a participial phrase cannot replace it.

Technically, a reduced relative clause that has become a participial phrase IS an adjectival phrase. 'Reduced relative clause' emphasises the origin (shortened from a full relative clause), while 'adjectival/participial phrase' describes the grammatical function (modifying a noun). In grammar teaching, both terms are used interchangeably for these structures.

Yes, both defining and non-defining relative clauses can be reduced. Non-defining: My sister, who is living in Paris, is a chef. → My sister, living in Paris, is a chef. Note that non-defining reduced relatives keep the comma. Non-defining reduction is less common and mainly found in formal or literary writing.

A perfect participle (having + past participle) is used when the action of the reduced relative clause happened before the main clause: The scientist having published the results withdrew from the conference. This is an advanced and mainly literary/formal structure. More commonly, the past participle alone is used. The perfect participle emphasises that one event clearly preceded the other.

Generally, yes. Reduced relative clauses are a feature of formal written English (academic papers, news reports, legal documents). In everyday speech, full relative clauses are more common: the car that is parked vs the car parked. However, some reduced forms are very common even in informal English: a sleeping baby, a broken window — these function almost as compound nouns.

Attributive adjectives come before the noun (a sleeping baby) while reduced relative clauses typically come after the noun (the baby sleeping in the cot). Many participles have become established as pre-noun adjectives: a broken heart, a running engine. Long participial phrases always follow the noun: The woman standing next to John (not The standing-next-to-John woman).

They create concise, dense information packaging. Instead of: Researchers who are working in the field of climate science have identified... → Researchers working in the field of climate science have identified... The reduced form is more economical and increases text density. Nominalisations and participial phrases together give academic writing its characteristic packed style.

Yes. At FCE (B2), sentence transformation tasks test this: 'The car which is parked here is mine.' → 'The car parked here is mine.' At CAE/CPE (C1/C2), more complex participial structures are assessed in writing tasks. IELTS Writing at Band 7+ shows reduced relative clauses and participial phrases as natural features of high-quality academic prose.