Here are few tests to identify a relative clause in a sentence. A particular test may not conclusively tell if the clause is relative, so it’s advisable to apply more than one to be doubly sure.
This post covers how to identify relative clause. Learn how to identify other dependent clauses as well. (In case you’re used to seeing only three dependent clauses, there are four.)
1. Is the marker word one that introduces a relative clause?
(A marker word, also called introductory word, introduces or begins a dependent clause.)
Relative clauses are introduced by marker words who, whom, whose, that, which, when, where, and why.
If the marker word of the dependent clause under investigation is from the above list, the dependent clause could be a relative clause.
Since the number of marker words are limited, you can memorize them all, but beware that a marker word that introduces relative clause may introduce noun or adverb clause as well. This limitation though is not difficult to overcome as only few marker words overlap. Only when and where introduce relative clause as well as adverb clause. And only who, whom, whose, that, which, when, where, and why introduce noun clause as well as relative clause. (The two links take you to examples of how each marker word can introduce two different clauses.)
Another challenge with this approach is that a relative clause may not even have a marker word.
1.1. A relative clause may not have a marker word
All marker words but whose can be dropped in a relative clause under certain conditions. (Read: When relative pronoun can be dropped and when relative adverb can be dropped?) Examples:
Don’t ask questions (which) people can’t or don’t want to answer. [which can be dropped]
He is a person (whom) you can disagree with and he won’t mind.
She may be assigned the project (that) she worked on last year.
How do you identify them without a marker word?
When you see a sentence-like unit (people can’t or don’t want to answer) immediately after a noun or noun phrase (questions), it’s a relative clause with its marker word dropped.
This comes with a small caveat though. Marker word that in noun clause too can be omitted, leading to a dependent clause that looks like a sentence. But here the clause usually follows a verb – and not noun or noun phrase. Examples:
She said she would call later. [that has been omitted. Noun clause follows verb said.]
I know he’s telling the truth.
2. Does the clause describe a noun phrase and follows it?
If the answer is yes, it’s a relative clause.
In all the examples, the clause describes the noun phrase (in blue font) and immediately follows it. Hence all the clauses are relative clauses.
Those who live in a glass house don’t throw stones.
I’m a living example of the dictum that an hour in the morning is worth two in the evening.
Greenhouse gases, which originate mainly from human activities such as transportation, electricity, and industry, are warming our planet to a dangerous level.
I invested in ten different companies, three of which returned losses. [Marker word may be preceded by numerals.]
It’s difficult to advise a person on a matter in which she is an expert. [Marker word may be preceded by prepositions.]
So, whenever you see a clause next to a noun phrase, it’s most likely a relative clause. You should then confirm it by seeing if it’s describing the noun phrase.
2.1. Sometimes a relative clause may describe an entire clause
A relative clause starting with which can function in two ways. Besides describing a noun or noun phrase, it can describe the entire preceding clause. In the latter function, it’s called sentential relative clause and is always preceded by a comma.
My dog, which is a German Shepherd, likes playing fetch. [Regular relative clause that comes after the noun phrase My dog and describes it]
My dog snarled at me, which came as a surprise to me. [Sentential relative clause. Here, the clause doesn’t describe My dog; it describes My dog snarled at me. After all, the dog didn’t come as a surprise; its snarling did.]
Now, marker word which can start a noun as well as a relative clause. But if you come across a sentential relative clause like which came as a surprise to me, most of your tests for both dependent clauses will fail. If that’s the case, check if the clause is modifying the preceding clause and has a comma before it. If yes, then it’s a relative clause – a sentential relative clause to be more precise.
3. Does the clause begin a sentence?
If the answer is yes, it can’t be a relative clause. This test will help you eliminate the option of relative clause.
Unlike an adverb clause or a noun clause, a relative clause can never begin a sentence.
What you did was beyond our wildest expectations. [Noun clause begins a sentence]
Because it was raining outside, I exercised indoors. [Adverb clause begins a sentence]
4. Rule out other dependent clauses
You can also identify a relative clause by ruling out the possibility of other three dependent clauses. How do you do that? Refer to the posts on how to identify noun, adverb, and comparative clause linked to earlier.
To end, while applying above tests, remember what was mentioned at the beginning of the post: A particular test may not conclusively tell if the clause is relative. It’s better to apply more than one to be doubly sure.
