英文關係子句 | Relative Clauses: 10 Rules Every Taiwan Learner Needs (2026)

Roughly 70 percent of GEPT and IELTS grammar test-takers in Taiwan report that relative clauses are among their biggest stumbling blocks — and based on the writing I see from adult learners here, that number is no surprise. The rules look simple on paper. But the moment a sentence has more than one clause, most people freeze and either drop the relative pronoun entirely or pick the wrong one. This guide breaks down the full system so you never have to guess again.

Who, which, and that are the three most common relative pronouns in English

什麼是關係子句？[What Is a Relative Clause?]

A relative clause is a dependent clause — meaning it cannot stand alone as a sentence — that gives extra information about a noun in the main clause. It “relates” back to that noun using a relative pronoun (who, which, that, whose, whom) or a relative adverb (where, when, why).

In Chinese, the equivalent structure puts the modifying information before the noun using 的 — for example, 住在台北的老師 (“the teacher who lives in Taipei”). English simply places the same information after the noun instead of before it. Once you see that parallel, the logic clicks into place.

Every relative clause contains three elements:

• An antecedent — the noun being modified (e.g., “the teacher”)
• A relative pronoun or adverb — the link word that introduces the clause (who, which, that, whose, whom, where, when)
• A verb phrase — what the clause says about the antecedent (“lives in Taipei”)

The result: The teacher who lives in Taipei is my favourite.

Notice that the clause “who lives in Taipei” cannot stand on its own. It depends on the noun “teacher” to have any meaning. That dependency is the defining characteristic of every relative clause.

Defining and non-defining relative clauses follow different punctuation rules

關係代名詞怎麼選？[Which Relative Pronoun to Use]

The single most important decision in any relative clause is which pronoun to use. The table below covers the cases that come up again and again in GEPT writing and IELTS essays:

One point that catches nearly every intermediate learner: you cannot use “that” in non-defining relative clauses — the type that use commas. This rule appears in every grammar book, yet it is the most violated one in written exams. We cover exactly why in the next section.

Most Taiwan learners first encounter relative clauses in junior high school English class

限制性 vs 非限制性子句 [Defining vs Non-Defining Relative Clauses]

This is where Taiwan learners consistently lose marks — not from ignorance, but from not understanding why the comma changes everything.

A defining relative clause (also called a restrictive clause) tells you exactly which person or thing is meant. Remove it and the sentence loses its essential meaning — you no longer know what is being talked about:

The employee who arrived late was warned.
Remove it: “The employee was warned.” Which employee? We have no idea. The clause is not optional — it defines which employee we mean.

A non-defining relative clause (also called a non-restrictive clause) adds extra information about something already clearly identified. It sits inside commas, and the sentence stays grammatically correct and semantically complete without it:

My manager, who has worked here for 20 years, is retiring next month.
Remove it: “My manager is retiring next month.” Perfectly clear. The clause is bonus information — nice to know, but not essential.

Three non-negotiable rules for non-defining relative clauses:

• Always use commas — one before the clause, one after (or just one before if the clause ends the sentence).
• Never use “that” — use “who” for people and “which” for things.
• Never attach a non-defining clause to an indefinite noun like “a woman” or “some books.” Non-defining clauses require a specific, already-identified noun.

Writing your own relative clause examples is the fastest way to make them stick

省略關係代名詞 [When You Can Drop the Relative Pronoun]

English has a shortcut that surprises many learners from a Chinese-speaking background: in defining relative clauses, you can often omit the relative pronoun entirely. The key condition is that the pronoun must be the object of the clause, not the subject.

Compare these two sentences:

• The book that I read was excellent. → “that” is the object — there is another subject (“I”) right after. You can drop it: “The book I read was excellent.” ✅
• The book that sits on the shelf is mine. → “that” is the subject — it is followed immediately by the verb “sits.” You cannot remove it: ✗ “The book sits on the shelf is mine.”

The simple test: if a new subject (I, she, they, we) appears right after the relative pronoun, the pronoun is the object and can be dropped. If the clause verb follows the pronoun directly, the pronoun is the subject — keep it.

Omitting the pronoun is extremely common in spoken English and informal writing. In formal writing and standardised tests like GEPT or IELTS, including the pronoun is the safer choice.

Non-defining relative clauses always require commas — the rule most test-takers miss

Whose 和 Whom 的進階用法 [Mastering Whose and Whom]

These two relative pronouns cause more confusion than all the others combined. Here is the sharpest way to think about each of them.

Whose shows possession. It replaces “his,” “her,” “its,” or “their” plus a noun. If you can substitute one of those phrases back in and have a grammatical sentence, “whose” is the correct choice:

• I know the woman. Her dog won the prize. → I know the woman whose dog won the prize. ✅
• They found the car. Its engine was damaged. → They found the car whose engine was damaged. ✅

A common misconception is that “whose” can only refer to people. It works perfectly well for things — and using it for objects actually produces cleaner, more natural sentences than the alternative “of which.”

Whom is the object form of “who.” The test: replace the pronoun with “him” or “her.” If that works naturally, use “whom.” If you need “he” or “she,” use “who”:

• I contacted the manager. → I contacted him. → The manager whom I contacted replied quickly. ✅
• The manager gave the presentation. → He gave it. → The manager who gave the presentation is retiring. ✅

In everyday spoken English, “whom” is increasingly replaced by “who” even by native speakers. For formal writing — academic essays, business reports, GEPT Advanced — knowing the distinction will put you ahead of 90% of test-takers.

Practice building sentences with whose and whom to master advanced relative clauses

台灣學習者最常犯的 5 個錯誤 [5 Mistakes Taiwan Learners Consistently Make]

After years of working with adult English learners in Taipei, these are the five errors I see on a near-weekly basis. Internalise these five fixes and your written English will immediately sound more natural.

1. Using “which” for people.

❌ The teacher which helped me was incredibly patient.
✅ The teacher who helped me was incredibly patient.

2. Missing commas in non-defining clauses.

❌ My colleague Sarah who lives in Tainan is coming to Taipei this weekend.
✅ My colleague Sarah, who lives in Tainan, is coming to Taipei this weekend.

3. Using “that” in a non-defining clause.

❌ My laptop, that I bought last month, keeps overheating.
✅ My laptop, which I bought last month, keeps overheating.

4. Doubling the pronoun (a direct Chinese transfer).
In Chinese, the subject of a relative clause is sometimes restated. English never does this.

❌ The student who she studied every night passed the exam.
✅ The student who studied every night passed the exam.

5. Limiting “whose” to people only.

❌ The building of which the roof collapsed was demolished. (technically correct, but clunky)
✅ The building whose roof collapsed was demolished.

Understanding how complex sentences are built goes beyond relative clauses alone. Our guide to passive voice in English shows how sentence structure changes when the subject and object swap roles — a pattern that often appears inside relative clauses in academic writing.

The key to relative clauses is understanding their function, not just memorising pronouns

練習例句：10 個完整例句 [10 Sentences to Practise

The fastest way to lock in these rules is to work with real examples and then write your own. Read each sentence below, identify the relative pronoun, and decide whether the clause is defining or non-defining before checking the note.

1. The café that opened last month has already become my favourite breakfast spot. (defining — tells us which café)
2. Dr. Chen, who has treated my family for fifteen years, is finally retiring. (non-defining — Dr. Chen is already identified; commas required)
3. I returned the book I borrowed from the school library. (defining, pronoun omitted — “I” follows, so “that” is the object and optional)
4. The app which my company developed won a design award last year. (defining — which one? the one my company built)
5. She is the colleague whose presentation impressed the entire board. (defining — whose = her)
6. The MRT station where we first met was renovated in 2023. (defining — “where” as a relative adverb)
7. The professor whom everyone admires will give a public lecture on Friday. (defining — formal written style; “whom” because “everyone admires him”)
8. My parents, who grew up in Tainan, still prefer southern-style beef noodles. (non-defining — parents are already clearly identified)
9. The project that I have been working on for six months is finally complete. (defining — which project? the one I have worked on)
10. Taipei 101, which was once the world’s tallest building, remains one of the city’s most recognised landmarks. (non-defining — “that” is wrong here; Taipei 101 is a unique, named building)

Sentences 2, 8, and 10 are non-defining. Pay close attention to where the commas sit in each one. Sentences 1, 4, 5, 7, and 9 are defining. Sentence 3 omits the relative pronoun because “I” follows immediately, making “that” the object — safely removable. Sentence 10 is a useful reminder: unique proper nouns (named buildings, cities, famous people) almost always require non-defining clauses because the noun is already fully identified.

Once you are comfortable with relative clauses, the logical next step is mastering concession clauses — the “although,” “despite,” and “however” structures that let you present two contrasting ideas in a single, sophisticated sentence. That combination — relative clauses for precision, concession clauses for nuance — is what separates intermediate writing from advanced English.

Sources

1. British Council — Relative Clauses Grammar Reference — Authoritative guide to defining and non-defining relative clauses with examples.
2. Cambridge Dictionary Grammar — Relative Clauses — Full reference for relative pronoun usage in British English, including “whose” and “whom.”
3. EnglishGrammar.org — Relative Clauses — Practice-focused resource with exercises for self-study.