6.3 Relative Clauses, Gerunds & Infinitives
Key Takeaways
- Who/whom/whose refer to people (subject/object/possession); which refers to things; that can refer to either but only in restrictive clauses; where and when refer to places and times.
- Restrictive clauses (no commas) identify which noun is meant and can use 'that'; non-restrictive clauses (set off by commas) add extra detail about a noun already identified.
- Some verbs take only a gerund (enjoy, avoid, finish, suggest), some take only an infinitive (want, decide, plan, agree), and this pairing must be memorized verb by verb.
- A small set of verbs (stop, remember, try) take either form with a real change in meaning -- check whether the sentence describes a completed action or a purpose/future obligation.
- Identify the anchor word first -- the noun for a relative clause, the first verb for a gerund/infinitive choice -- then apply its specific rule rather than guessing from the sentence's general meaning.
This section covers two grammar areas that frequently overlap on STEP: relative clauses, which add descriptive information about a noun using a relative pronoun, and the gerund/infinitive system, which governs what form a verb takes when it follows another verb.
Relative Pronouns: Who, Whom, Which, That, Whose, Where, When
A relative clause attaches extra information to a noun using a relative pronoun. The choice of pronoun depends on what the pronoun refers to and what role it plays inside its own clause.
| Pronoun | Refers To | Example |
|---|---|---|
| who | people (subject of the clause) | The professor who teaches statistics is on leave. |
| whom | people (object of the clause) | The candidate whom the panel selected starts Monday. |
| which | things or animals | The report, which was submitted late, still scored well. |
| that | people or things (restrictive clauses only) | The laptop that I bought last month broke down. |
| whose | possession (people or things) | The employee whose badge was lost had to be reissued one. |
| where | places | This is the building where the orientation is held. |
| when | times | 2019 was the year when the new curriculum began. |
"Who" versus "whom" is a frequent trap: use "who" when the pronoun is the subject of its own clause (it performs the action) and "whom" when it is the object (the action is done to it). A quick test is to rephrase the clause as a statement using "he/him" or "she/her" -- if "him" or "her" fits, "whom" is correct; if "he" or "she" fits, "who" is correct.
Restrictive vs. Non-Restrictive Clauses
Whether a relative clause takes commas depends on whether the information is essential to identifying the noun (restrictive, no commas) or simply adds extra detail about a noun that is already identified (non-restrictive, set off by commas).
- Restrictive (no commas; "that" is acceptable): The students who missed the deadline will not receive credit. -- the clause tells us which students; removing it changes the meaning.
- Non-restrictive (commas required; "that" is not used): My eldest brother, who works as a civil engineer, is visiting next week. -- "my eldest brother" is already a unique, identified person, so the clause simply adds extra information and could be removed without changing who is being discussed.
A practical test: read the sentence without the relative clause. If the sentence still identifies exactly the same person or thing, the clause is non-restrictive and needs commas. If removing the clause makes the reference vague or changes which noun is meant, the clause is restrictive and takes no commas.
Gerunds vs. Infinitives
When one verb is followed by another verb, the second verb must take one of two forms: the gerund (verb + -ing, functioning as a noun) or the infinitive (to + base verb). Which form is correct depends entirely on the first verb -- this, like dependent prepositions, must largely be memorized rather than derived from a rule.
| Category | Common Verbs | Example |
|---|---|---|
| Gerund only | enjoy, avoid, finish, suggest, consider, mind, deny, postpone | She finished writing the report before lunch. |
| Infinitive only | want, decide, plan, agree, hope, offer, promise, refuse | They decided to reschedule the meeting. |
A smaller group of verbs can take either form, but the choice changes the meaning of the sentence:
| Verb | + Gerund (meaning) | + Infinitive (meaning) |
|---|---|---|
| stop | end a habit or activity: He stopped smoking. | pause in order to do something else: He stopped to smoke. |
| remember | recall a past event: She remembered locking the door. | not forget a future obligation: She remembered to lock the door. |
| try | experiment with something: Try restarting the computer. | make an effort: Try to finish before the deadline. |
Because these meaning-change verbs are a favorite STEP distractor, always check whether the sentence describes a completed action being recalled or discussed (gerund) or a purpose/future obligation (infinitive) before choosing.
Putting It Together
Relative clauses and the gerund/infinitive system both reward the same test-taking habit: identify the anchor word first -- the noun being described, for a relative clause, or the first verb, for a gerund/infinitive choice -- and then apply the specific rule tied to that anchor rather than guessing from general sentence meaning. On STEP, distractor options are built to look grammatically plausible in isolation, so the anchor word is what narrows the four choices down to one correct answer.
My eldest brother, ______ works as a civil engineer in Jeddah, is visiting us next week.
The laptop ______ I bought last month has already stopped working properly.
The manager suggested ______ the meeting until all departments could attend.
On his way to the office, Khalid stopped ______ a cup of coffee before continuing his commute.