Grammar Lesson of the Month: Defining and Non-Defining Relative Clauses (+ Choosing the right proficiency exam)

Students are often confused about when to use THAT and when to use WHICH in a Relative Clause. Do you know when to use each, and when to use commas with a Relative Clause? The CISL Blog is exploring this, then using Relative Clauses to help you decide between the English proficiency tests that we offer: IELTS, Cambridge CAE, Cambridge FCE, and TOEFL.

Non-Defining and Defining Relative Clauses

A general rule is that we use THAT for Defining Clauses and WHICH for Non-Defining Clauses.

Non-Defining Relative Clauses

Non-Defining Relative Clauses provide us more information about someone or something . . . but this information is considered “extra”: it does not define the noun in the sentence.


Many think San Diego, which is a city in Southern California, has the best weather in the United States.

Surfing, which is done by many San Diegans, is a common activity.

San Francisco, which is located in Northern California, is considered a highly culturally diverse city.

Wine tasting, which takes places in nearby Napa and Sonoma, is a common activity for CISL SF students.

Notice that in these sentences, the information between the commas is extra: it does not provide us the definition of San Diego, Surfing, San Francisco, or Wine tasting.

Surf’s up!

Defining Clauses

Defining Clauses, as the name suggests, provide us with the definition of the noun in the sentence: they specify the noun or help to distinguish it from others.

Notice that we can also use WHO when the noun is a person. In casual speech, we use both: for more formal writing, it is considered best to use WHO and not THAT.


San Diegans who/that don’t go to the beach are uncommon.

San Diego has many restaurants that offer beautiful views of the ocean.

San Franciscans are people who/that love culture and great food.

San Francisco has many restaurants that serve fusion food.

Vietnamese with a twist? Restaurants like the Slanted Door offer delicious takes on vibrant cuisines. Photo from Slanted Door.

Further Examples

Looking at Defining and Non-Defining Relative Clauses side-by-side is a great way to see the differences between these two types of Relative Clauses.

Here are some examples. Notice how we only have the option of WHO or THAT with Defining Clauses.

Dogs which are dangerous are not allowed. (Only dogs that are dangerous are not allowed. The other dogs are probably allowed.)

Dogs, which are dangerous, are not allowed. (All dogs are dangerous and are not allowed.)

Celebrities, who are rich, can buy anything. (All celebrities are rich and can buy anything.)

Celebrities who/that are rich can buy anything. (Only some celebrities are rich, and these celebrities can buy anything.)

San Diegans who/that love to swim go to the beach often. (The San Diego residents who like to swim go to the beach. But not everybody loves to swim and not everyone goes to the beach.)

San Diegans, who love to swim, go to the beach often. (All San Diegans love to swim and go to the beach.)

Notice how Non-Defining Relative Clauses are always separated from the rest of the sentence by commas, unlike Defining Relative Clauses, which do not use this punctuation.


Choosing Between IELTS, TOEFL, and Cambridge FCE or CAE

These days, there are many exams that test your English proficiency. CISL is proud to offer test preparation courses for the CAE, FCE, IELTS, and TOEFL exams. Which test is perfect for you? Read on to learn a little more about each test.


Test of English as a Foreign Language

The TOEFL exam is a roughly three-hour test that measures your ability to understand English in an academic setting.

The test, which is computer based, has four sections: Reading, Writing, Listening, and Speaking.

The Reading section is a test that is designed to test your ability to read quickly.

The Reading section, which has questions in multiple-choice format, has 3-5 readings.

The score, which is valid for two years, uses a 0 – 120 point scale.


Cambridge CAE

Certificate of Advanced English 

The CAE Exam, which measures your ability to understand English in an academic and business settings, is designed for students at the CEFR B2/C1 level. (For more information on the CEFR, which stands for “Common European Framework of Reference for Languages,” click here.)

There is one part of the test that is given on a separate day: the Speaking Test.

The test, which is roughly 4 hours total, also has Modules on Reading, Writing, and Listening.

Reading and Use of English, which includes grammar-based questions, is typically the more “feared” CAE Module.

To pass, students must correctly answer just 60% of the questions, which isn’t a lot! Click here for an explanation of Cambridge CAE and FCE scores, which can be confusing.


Cambridge FCE

First Certificate of English 

The FCE Exam, which is also offered by Cambridge, is designed for students who are at the CEFR B1/B2 level.

Also as with the CAE, the test is roughly 4 hours and has tests that are given either by computer or paper.

Both the CAE and FCE tests that are given by Cambridge test Reading, Writing, Listening, and Speaking.

The scoring is the same as with CAE, which can be explained in detail by a CISL teacher.

The score, which is valid for an indefinite amount of time, can sometimes “expire” depending on the standards of the company or organization that requires it.



International English Language Testing System 

Purpose: the IELTS Exam has two forms: Academic and General Training.

The Academic test/preparation exam, which is offered at CISL, is for those who want to enroll in universities and other institutions of higher education, as well as professionals who want to study or work in an English-speaking country.

IELTS is a test that is accepted by most Australian, British, Canadian, Irish, New Zealand and South African academic institutions.

The test, which is also a requirement for immigrating to Australia, New Zealand and Canada, is growing in popularity in the U.S.

Length: There are 3 sections that are given on one day (Reading, Writing, and Listening).  These sections last roughly 3 hours.

The Speaking Module, which is about 15 minutes, can be taken up to 7 days before or after the rest of the exam.

The score, which is on a scale from 1-9,  is not Pass/Fail. The accepted score varies with each company and university.

The score does not expire, however, some companies require you to have taken the test within a certain amount of time (usually 2 years).


For more information on CISL’s test preparation courses, click here.