Advanced Relative Clauses: Non-Finite and Reduced— C1 Grammar Exercises

The graph titled Annual Migration Patterns, drawn from census data spanning 1990 to 2020, illustrates a steady decline. The bracketed phrase modifies graph, but it carries no relative pronoun and no finite verb; it has been reduced. At C1, mastering these reductions is what allows your writing to move from competent to economical.

A non-finite or reduced relative clause is a relative clause in which the relative pronoun and an auxiliary or copula have been omitted, leaving behind a participle, an infinitive, or a bare adjective phrase. The clause continues to modify a noun, but the connection becomes implicit. This pattern is the engine of dense academic, journalistic, and legal prose.

How reduction works

Reduction takes a finite relative clause (one with who/which/that and a tensed verb) and strips the linking machinery away. What remains depends on whether the original verb is active, passive, or a copular structure with be. The full-form mechanics are covered in defining relative clauses and defining and non-defining relative clauses; this page assumes you are comfortable with both.

The -ing form here is not a continuous aspect: it is the active participle in a non-finite clause, and it covers active meaning across all tenses. Only when the original verb is passive does the reduced form take the past participle.

Reducing active clauses with -ing

Use the -ing participle for any active verb in the original clause. The reduction is most natural when the clause expresses a general property, ongoing state, or future-oriented condition rather than a single completed past event.

• Passengers travelling with children may board first.
• Everyone working on the night shift receives an allowance.
• Companies operating in multiple jurisdictions face additional reporting requirements.

Reducing passive clauses with the past participle

When the original verb is passive, drop the relative pronoun and the form of be, leaving the past participle alone. This is the most common reduction in academic and news writing because it allows dense post-modification of nouns. For a fuller treatment of how participle phrases function beyond modifying nouns, see advanced participle clauses.

• The painting stolen from the Louvre has surfaced in Geneva.
• Treaties signed under duress are not legally binding.
• The medication prescribed by her doctor caused side effects.

Dropping be before adjectives and noun phrases

When the original clause has be followed by an adjective phrase, prepositional phrase, or noun phrase, the relative pronoun and be are deleted together.

• The students eligible for the scholarship must apply by June. (= who are eligible)
• Anyone unable to attend should notify HR. (= who is unable)
• The architect behind the project declined to comment. (= who is behind)

Infinitive relative clauses

A relative clause can also reduce to a to-infinitive. This pattern carries a sense of purpose, possibility, or futurity that participle reduction cannot. It is the natural choice after specific noun triggers.

• She was the first candidate to be interviewed.
• He is the only one to have completed the course.
• I need a quiet place to work.
• There's nothing to be gained from arguing.

After the first / only / last, the infinitive is the natural choice. The -ing form is grammatical but reads as awkward and is rarely produced by fluent writers.

Formal connectors that resist reduction

At C1, you also need control of the formal relative connectors that appear in academic, legal, and high-register prose. These structures cannot be reduced; the connector itself is doing essential grammatical and stylistic work.

Preposition + which / whom

The preposition moves to the front of the clause. The pronoun must be which for things or whom for people, never that, never who. If you are unsure which form is correct, see who vs whom.

• The colleague to whom I reported has retired. (less formal: who I reported to)
• The framework within which we operate is constantly evolving.
• This is the principle on which the entire argument rests.

Stranding the preposition at the end of the clause (who I reported to) is fully grammatical and now standard in most registers; fronting it (to whom I reported) signals a deliberately formal style. See preposition stranding vs fronting for when each is preferred.

Quantifier + of which / of whom

This structure adds information about a subset of a group already mentioned. It appears only in non-defining clauses and is preceded by a comma.

• The board has twelve members, most of whom are based in London.
• She published three novels, none of which sold well.
• The findings, many of which were unexpected, will be released next month.

whose and of which

Whose works for both people and things, though using it for inanimate things still feels slightly informal in some registers. Of which is the formal alternative for things, with the modified noun placed before the connector.

• A novel whose protagonist never speaks. neutral
• A novel the protagonist of which never speaks. very formal

Register at a glance

The same modifying idea can be expressed at three different registers. Reduced forms and formal connectors push the register up; full who/which clauses with stranded prepositions pull it down.

Common mistakes

Full vs reduced: when to choose which

Reduction is a register choice as much as a grammar one. Compressed forms dominate research papers, news leads, legal description, and product copy; full clauses are more typical of conversation and informal writing. For more on how register shapes structural choices, see formal and informal register.

Frequently asked questions

What is a reduced relative clause?

A reduced relative clause is a relative clause with the relative pronoun and an auxiliary or form of be removed, leaving a participle, infinitive, or bare adjective phrase that still modifies the noun. The man who is waiting reduces to the man waiting; the report which was published reduces to the report published. The clause is called "non-finite" because nothing in what remains is marked for tense.

What's the difference between -ing and past participle in reduced relative clauses?

The -ing participle replaces an active verb; the past participle replaces a passive one. Tourists visiting Paris means tourists who visit (active). Tourists welcomed by the mayor means tourists who were welcomed (passive). If you can rewrite the original with be + past participle, you need the past participle in the reduction.

Can you drop "who" or "which" from a relative clause?

Yes, but only when the relative pronoun is the subject of the clause and reduction is grammatically licensed. You drop who/which together with any form of be, leaving a participle or adjective phrase: the woman who is sitting there → the woman sitting there. You cannot drop the pronoun and keep a finite active verb: the report which published last week is wrong.

Can non-defining relative clauses be reduced?

Yes, when they describe a state, identity, or passive action. The painting, which was damaged in the fire, has been restored reduces to the painting, damaged in the fire, has been restored. The commas remain. Reduction is less natural with single-event active verbs in non-defining clauses, where the full form usually reads better.

What does "to whom" mean and when do you use it?

To whom is the formal version of who… to, used when whom is the object of the preposition to. The colleague to whom I reported means the same as the colleague who I reported to, but signals academic, legal, or high-register writing. The same pattern works with other prepositions: with whom, for whom, on which, in which. Never use that after a fronted preposition.

What's the difference between "whose" and "of which"?

Whose shows possession or association for both people and things and works in any register. Of which is a formal alternative for things only, with the noun placed before the connector: a novel whose protagonist never speaks ↔ a novel the protagonist of which never speaks. The of which version sounds heavily formal and appears mostly in academic and legal writing; whose is the safer default in almost every other context.

Quick summary

Related topics

• Defining relative clauses: the full-form foundation these reductions build on.
• Passive voice: advanced forms, closely linked, since most past-participle reductions are passive in origin.
• Nominalization: another compression strategy used alongside reduced relatives in formal writing.