Reduced relative clauses

A relative clause identifies or describes a noun: The proposal that was submitted on Friday is under review. When its meaning and grammar allow it, the clause can be shortened to The proposal submitted on Friday is under review. This compact form is a reduced relative clause. It is useful in reports and academic prose, but reduction is optional: a full clause is often clearer when the sentence is already dense.

Two common reductions

When the noun receives the action, remove the relative pronoun and the form of be, leaving a past participle:

The documents that were signed yesterday are ready.
The documents signed yesterday are ready.

When the noun performs an ongoing or characteristic action, a present participle can replace a relative clause with who/which + be + -ing:

Students who are applying late should email us.
Students applying late should email us.

The participle's meaning matters: documents signed by the director are passive; the director signing the documents is active. Do not choose the form by appearance alone.

The infinitive in descriptions of sequence or purpose

A to-infinitive can reduce a relative clause when a noun is described as the first, next, last, only or intended person or thing to do something:

Nia was the first person who noticed the error.
Nia was the first person to notice the error.

The next train that leaves from platform 4
The next train to leave from platform 4

This pattern is not a universal replacement for future relatives. The first person speaking could mean the first person who happens to be speaking; the first person to speak more clearly identifies the person whose turn comes first.

Defining and additional information

A defining relative clause tells us which person or thing is meant: The applicants interviewed yesterday will hear back soon. There are no commas because the interview detail identifies the group.

A non-defining clause adds information about an already identified noun and normally uses commas. It can sometimes be reduced too:

The bridge, which was built in 1890, is closed for repairs.
The bridge, built in 1890, is closed for repairs.

The commas remain because the phrase still adds extra information. Compare this with The bridge built in 1890 is closed, where the phrase may distinguish it from another bridge.

When reduction is not possible or not wise

Do not remove a subject relative pronoun and leave a finite verb behind:

~~The students study abroad need visas.~~
The students who study abroad need visas.
The students studying abroad need visas.

The second option changes the clause into a participle phrase; the first keeps a finite clause. Also keep the time relationship clear. The students who studied abroad last year is unambiguous; the students studying abroad last year can sound as though the study was in progress at another past moment. When a reduced phrase could have more than one attachment, use the full relative clause.

A participle clause at the start of a sentence is not automatically a reduced relative: Walking across the square, I saw Ana describes what I was doing. In The woman walking across the square is Ana, the participle phrase modifies woman. The grammatical role and punctuation distinguish the constructions.

The noun is the anchor

A reduced relative must attach clearly to the noun it describes. In Applicants selected for interview will receive an email, selected for interview modifies applicants. In The report published last month was revised, the phrase modifies report. If a long phrase sits too far away, readers may attach it to the wrong noun:

Ambiguous: We discussed the proposal with the consultants submitted last week.
Clear: We discussed the proposal submitted last week with the consultants.

When the modifier is long, a full relative clause can be easier to follow: the proposal that the consultants submitted last week.

Not every short phrase is a reduced relative. The people responsible for the error has an adjective phrase; the people waiting outside has a participle phrase; the people chosen for the project has a passive participle. All can modify a noun, but their internal forms differ. The participle form should preserve who performs or receives the action.

Reduced phrases can be non-defining, with commas: The old library, built in 1890, is being restored. Without commas—The library built in 1890 is being restored—the phrase may identify one library among several. The decision is about the information the reader needs, not merely the length of the phrase.

Use the full relative clause when the relationship is not obvious, when the relative pronoun has a different grammatical role, or when reduction would create a dangling modifier. A concise form is valuable only if the reader can immediately see which noun it describes and whether that noun acts or is acted upon.