For Grammar Rules about Defining Relative Clauses see my post September 22, 2013.
- RIHANNA sings a song with Eminem called ‘Monster’. There are Defining Relative Clauses in the chorus. Have a look:
Chorus
1. I’m friends with the monster that’s under my bed.
2. (I) Get along with the voices inside of my head.
3. You’re trying to save me.
4. Stop holding your breath.
5. And you think I’m crazy.
6. Yeah, you think I’m crazy (crazy).
The Relative clauses in Lines 1 & 2 are clearly Defining Relative Clauses because they are obviously necessary in the sentence. You know they are necessary because if you take them out, the sentences have no meaning:
I’m friends with the monster. 
I get along with the voices.
If a friend said to you, “I’m friends with the monster”, you would ask, “Which monster??”
The Defining Relative Clause tells us which monster.
If a friend said to you, “I get along with the voices”, you would ask, “Which voices??”
The Defining Relative Clause tells us which voices.
Also note that Rihanna sings about “THE monster”, “THE voices”. “THE” is the Definite (defining!) Article. We use THE when it is clear which noun we are talking about, but if we just say, “I’m friends with the monster”, it is NOT clear which monster. If we just say, “I get along with the voices”, it is NOT clear which voices. We need to define which monster and which voices. We need Defining Relative Clauses.
*** Defining Relative Clauses do not use commas because commas (like these brackets) separate the Relative Clause from the Independent Clause and we don’t want to separate the Relative Clause because the information is important for meaning.
*** Non-Defining Relative Clauses use commas because the Relative Clause provides extra, separate information (like extra information we sometimes put in brackets).
The song ‘Monster’, which I like, is sung by Rihanna and Eminem.
‘which I like’ is a Non-Defining Relative Clause. It doesn’t tell us which song. It’s extra information.
Rihanna and Eminem, who are very successful, sing a song called ‘Monster’.
‘who are very successful’ is a Non-Defining Relative Clause. It doesn’t tell us who Rihanna and Eminem are. It’s extra information about them.
Take out the Non-Defining Relative Clauses and the sentences have meaning:
The song ‘Monster’ is sung by Rihanna and Eminem.
Rihanna and Eminem sing a song called ‘Monster’.
I highly recommend that you sing the chorus of ‘Monster’ (video below) a few times until you know it well. Then, whenever you need an example of a Defining Relative Clause, one will be easy to recall.
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- Now, let’s look at two more Defining Relative Clauses.
Adam Levine & Maroon 5
- MAROON FIVE sing a song called ‘This Love’. The first few lines contain Defining Relative Clauses:
1. I was so high I did not recognize
2. The fire (which/that was) burning in her eyes,
3. The chaos that controlled my mind.
Here you can see that the Relative Clauses are vital for meaning. Take them out and the song has no clear meaning:
I was so high I did not recognize the fire, the chaos .. Which fire?? Which chaos??
*Note again the use of the Definite Article: THE fire, THE chaos.
I highly recommend that you sing the chorus of ‘Monster’ (click here for the video) and the lines from ‘This Love’ (lyrics video) a few times until you know them well. Then, whenever you need an example of a Defining Relative Clause, you will be able to recall one or more easily.
You could also check other examples in songs by clicking here.
If you have any questions or would like more examples, just leave a comment below.