Defining relative clauses — also called restrictive relative clauses — tell the reader exactly which noun you are talking about. Without the clause, the sentence either becomes unclear or changes its meaning entirely.

Consider the difference: 'Students who study abroad gain valuable experience' versus 'Students gain valuable experience.' The defining clause 'who study abroad' narrows the focus to a specific group. Remove it, and the sentence becomes too general. This is the core function of a defining clause: it identifies and restricts.

The main relative pronouns are 'who' (for people), 'which' (for things in formal writing), 'that' (for both people and things, but less formal), and 'where' (for places). In academic writing for IELTS and PTE, prefer 'which' over 'that' when referring to things — it reads as more formal and polished. However, 'that' is perfectly grammatical and is the only option after words like 'everything', 'something', or 'nothing'.

A crucial punctuation rule: defining relative clauses do NOT take commas. The clause is essential to the noun's identity, so nothing separates it. Compare: 'Policies that reduce emissions are popular' (defining — which policies? the ones that reduce emissions) with 'Policies, which reduce emissions, are popular' (non-defining — the writer assumes you already know which policies). This distinction will be explored in the next lesson.

One more useful feature is the contact clause. When the relative pronoun functions as the object of the clause, you can omit it entirely. 'The report that I read was insightful' becomes simply 'The report I read was insightful.' This is perfectly acceptable in academic writing and makes your sentences more concise.

Why does this matter for your score? IELTS examiners and PTE scoring algorithms assess grammatical range. If every sentence follows a simple subject-verb-object pattern, your score stalls around Band 5.5. Defining relative clauses let you embed information within a single sentence, demonstrating control of complex structures — a hallmark of Band 6.5 and above in Grammatical Range.

Non-defining relative clauses add extra information about a noun that the reader can already identify. Unlike defining clauses, they do not change the sentence's core meaning — they simply provide additional detail.

Consider: 'Barcelona, which hosted the 1992 Olympics, attracts millions of tourists each year.' The reader already knows which city you mean — Barcelona. The relative clause adds a bonus fact. Remove it, and the sentence still makes complete sense: 'Barcelona attracts millions of tourists each year.' This is the key test: if the clause can be removed without losing the noun's identity, it is non-defining.

The punctuation is non-negotiable: non-defining clauses are always surrounded by commas. This signals to the reader — and to the examiner — that the information is parenthetical. Forgetting the commas changes the clause type entirely, which can alter meaning.

Two rules separate non-defining clauses from defining ones. First, you cannot use 'that' — only 'who' (for people), 'which' (for things), 'where' (for places), or 'whose' (for possession). Second, the relative pronoun can never be omitted, unlike in defining contact clauses.

There is a particularly powerful variation worth mastering: using 'which' to refer to an entire preceding clause, not just a single noun. For example: 'The government subsidised electric vehicles, which significantly reduced urban air pollution.' Here, 'which' refers to the whole idea of subsidising vehicles — not just to 'vehicles.' This structure is extremely useful in IELTS Task 2 and PTE Write Essay tasks when you want to add a consequence or comment on a point you have just made.

For your exam score, non-defining relative clauses demonstrate the ability to layer information elegantly. They show the examiner that you can add detail without writing a new sentence — a hallmark of Band 7 writing. Use them to include background facts, qualifications, or examples mid-sentence.

Reduced relative clauses are a powerful way to make your writing more concise and sophisticated. They remove unnecessary words — specifically the relative pronoun and the auxiliary verb — while preserving the full meaning.

The principle is straightforward. When a defining relative clause contains a form of 'be' followed by a participle (present or past), you can remove both the relative pronoun and 'be'. Compare: 'The students who are sitting in the front row' becomes 'The students sitting in the front row.' 'The policy that was introduced last year' becomes 'The policy introduced last year.' The reduced version is shorter, sharper, and more common in academic writing.

This works in several patterns. Active clauses with a present participle reduce easily: 'Factors that contribute to inflation' becomes 'Factors contributing to inflation.' Passive clauses reduce even more naturally: 'The data that was collected over ten years' becomes 'The data collected over ten years.' In both cases, the reduced form sounds more polished and professional.

However, reduction is not always possible. You cannot reduce a clause that contains a modal verb — 'Students who must attend the lecture' cannot become '*Students must attend the lecture' (the meaning changes entirely). You also cannot reduce when the verb has no 'be' auxiliary and is not in the simple present or past — 'The man who has three children' does not reduce neatly. The key question is: can you remove the relative pronoun and a form of 'be' without changing the meaning? If yes, reduce. If no, keep the full clause.

Why learn this for your exam? Examiners reward economy of expression. A paragraph that communicates the same ideas in fewer words — without sacrificing clarity — demonstrates Band 7-level control. Reduced relative clauses are one of the most reliable ways to achieve this. They are especially valuable in IELTS Task 1 process descriptions and PTE summaries, where conciseness directly affects your score.