Guide Exercises

Introduction

You already know relative clauses: "the man who is talking to Sarah," "the book which was written by her." This page is about trimming them down — dropping the relative pronoun and the auxiliary verb, and letting a bare participle do the work instead: "the man talking to Sarah," "the book written by her."

This is called reducing the clause, and the result is called non-finite, because the verb inside it no longer marks tense at all — "talking" and "written" don't tell you when anything happened, only what's happening to the noun in front of them. That trade-off is exactly why this structure matters at C1: it's tighter, more economical, and everywhere in journalism, reports, and formal writing — but that missing tense information is also exactly where this structure quietly breaks if you're not careful about which clauses can lose it and which ones can't.

The Core Forms

Pattern 1 — Present participle (-ing), active meaning

Drop the relative pronoun and "be," and put the verb into -ing form
The scientist who is presenting the new research is highly respected.
→ The scientist presenting the new research is highly respected.

Passengers who are travelling without a valid ticket will be fined.
→ Passengers travelling without a valid ticket will be fined.

Pattern 2 — Past participle (-ed / irregular), passive meaning

Drop the relative pronoun and "be," and keep the verb in its past participle form
The letter which was sent last week never arrived.
→ The letter sent last week never arrived.

Animals that are found in this region are protected by law.
→ Animals found in this region are protected by law.

Pattern 3 — To-infinitive, after a closed set of triggers

After a superlative, an ordinal number, or only/first/last/next, the relative clause can reduce to a to-infinitive instead of a participle
She was the only witness who saw the accident.
→ She was the only witness to see the accident.

Tom was the first runner who crossed the finish line.
→ Tom was the first runner to cross the finish line.

Pattern 4 — Bare adjective or prepositional phrase

When the relative clause is just "be/seem/appear" plus an adjective or a prepositional phrase, you can drop the pronoun and the verb entirely
The product, which seemed perfect in every way, still failed in the market.
→ The product, perfect in every way, still failed in the market.

The office, which is on the third floor, has excellent natural light.
→ The office, on the third floor, has excellent natural light.

The Real Rule: Why This Doesn't Generalize

1

Only subject relative clauses can reduce this way — clauses where the relative pronoun stands in for the subject of its own clause. "The book which was written by her" reduces because "which" is the subject of "was written." A clause where the pronoun is the OBJECT — "the man who(m) I met yesterday" — cannot become a participle phrase at all; there's a completely different, much simpler reduction available for those, covered further down.

2

A modal verb blocks this kind of reduction entirely, because a participle has no way to carry a modal's meaning. "The technician who can fix this model" cannot become "the technician fixing this model" — that swap doesn't shorten the sentence, it changes it, replacing "is able to fix" with "is currently fixing." When a modal is doing real work in the clause, you simply keep the full form.

3

Reduction throws away tense and aspect information, so it's a bad move whenever that timing detail is actually part of the meaning. "The plane which had just landed was towed to the gate" reduced to "the plane landing was towed to the gate" muddies exactly when the landing happened — it now reads as if the plane might still be in the air. If the specific timing matters, leave the clause in its full form.

4

The to-infinitive pattern (Pattern 3) is not a general substitute for "who/that" — it only appears after that specific closed set of triggers: superlatives, ordinals, and only/first/last/next. An ordinary subject relative clause with no such trigger doesn't get this treatment: "the woman who runs this company" cannot become "the woman to run this company" just because it feels tidy — there's nothing here licensing a to-infinitive.

5

Stative verbs (know, own, believe, want, prefer, and similar verbs that don't naturally occur in the progressive) resist -ing reduction, for the same reason they resist the progressive tense everywhere else in English. "The employee who knows the password" turning into "the employee knowing the password" doesn't break any rule of relative-clause grammar exactly — it's just an awkward, non-native-sounding result, because "knowing" was never a comfortable form for this verb to begin with.

Common Errors

Error 1 — Turning an object relative clause into a participle. Participle reduction only works for subject relative clauses — the fix here isn't a participle, it's simply dropping the pronoun.

✗ The keys losing under the couch were finally found.
✓ The keys I lost under the couch were finally found.

Error 2 — Losing a modal in the process of reducing.

✗ The technician fixing this exact model has plenty of experience.
✓ The technician who can fix this exact model has plenty of experience.

Error 3 — Reducing a clause where the tense actually matters.

✗ The plane landing was immediately towed to the gate.
✓ The plane that had just landed was immediately towed to the gate.

Error 4 — Using a to-infinitive with no real trigger.

✗ The woman to run this small business is my aunt.
✓ The woman running this small business is my aunt.

Error 5 — Forcing -ing onto a stative verb.

✗ The professor knowing every detail of the case testified first.
✓ The professor who knew every detail of the case testified first.

Error 6 — Dropping "not" instead of keeping it before the participle.

✗ The passengers having boarding passes should proceed to gate 12. (reverses the meaning!)
✓ The passengers not having boarding passes should proceed to gate 12.

Error 7 — Choosing the wrong participle for the voice. The contract doesn't sign itself.

✗ The contract signing by both parties is now legally binding.
✓ The contract signed by both parties is now legally binding.

Register and Usage

Reduced relative clauses, especially Patterns 1 and 2, are a hallmark of formal, written English — news reports, academic writing, and official documents lean on them constantly for compactness ("Police are searching for a man seen leaving the building"). In relaxed conversation, full relative clauses with "who/that/which" are far more common; stacking reduced clauses into everyday speech can come across as clipped or oddly formal.

Pattern 3 (the to-infinitive after only/first/superlatives) is the exception — it's natural and common in both speech and writing, since it's less about formality and more about a fixed, everyday way of phrasing "the first one to..." or "the only person to...".

Don't Confuse This With: Pronoun-Deletion and Adverbial Participle Clauses

The term "reduced relative clause" actually covers two quite different things, and it's worth keeping them apart. What this page has focused on is non-finite reduction: turning a subject relative clause into a participle, which strips out tense entirely. But there's a second, much simpler kind of reduction that applies to OBJECT relative clauses: just deleting the relative pronoun, with the verb staying fully finite and unchanged. "The book (that) you gave me was excellent" — the clause is still "you gave me," complete with its own tense; nothing about the verb has changed, only the pronoun has disappeared. These two look similar because both involve "removing something," but one removes a function word from an otherwise intact clause, and the other reshapes the verb itself.

It's also worth telling reduced relative clauses apart from participle clauses that modify the whole sentence rather than a specific noun. "The man walking home saw an accident" is a reduced relative clause — "walking home" describes "the man." "Walking home, I saw an accident" is an adverbial participle clause — "walking home" describes the circumstances of the whole event, roughly meaning "while I was walking home." Same -ing shape, genuinely different job.

The same underlying instinct — drop what the reader can already reconstruct — shows up again in a different family of structures on the Advanced Ellipsis page ("whether right or wrong," "if any," "if anything").

Exercises

EXERCISE:

Exercise 1 — Transformation

Reduce each sentence if possible. If it cannot be reduced to a participle, simply type "Cannot be reduced" — think about why before you check your answer.

1. "The scientist who is presenting the new research is highly respected." →
2. "The letter which was sent last week never arrived." →
3. "The man who can fix any car works at that garage." →
4. "She was the only student who solved the puzzle." →
5. "The employees who don't have security badges must check in at the front desk." →
6. "The house which stands on the corner has been empty for years." →
7. "The man who I spoke to yesterday turned out to be my new neighbor." →
8. "Tom was the fastest runner who finished the race." →