 Hello everyone, how are you today? This is Marc. I'm doing great. Thanks for asking. The girl who was singing is my cousin. The girl to whom you spoke told me she was from India. Those are the stairs that will take you to the first floor. The reason why he called you is because he missed you. My apartment, which cost me a lot, will be sold soon. In this lesson, we're going to take a look at relative classes, so stay tuned. Right, relative classes. When you have two or more sentences and you wish to join them and give more information about something, then you use relative classes. We use why for reason, we use when for time, we use where for location, we use whom or even that for people and which or that for objects. One other, who's for possession. So there can be defining and non-defining relative classes. Defining relative classes tells us which subject we're talking about. Just like my example, the girl who was singing is my cousin. So for example, we can give or we can ask ourselves a question. So who was singing? The girl. So the girl was singing and who is she? My cousin. So who tells us who the subject is, right? In a formal context, we can put the preposition before the relative classes. For example, the girl to whom you spoke told me she was from India. But we can even say in informal English, the girl who you spoke to told me she was from India. Or even the girl that you spoke to told me she was from India. But even the girl you spoke to was from India. So you can see, we can have even four versions of the same sentence. It depends on what context you want to use it. So if the subject is an object like stairs in this case, we use which or that. Which is more formal than that. So those are the stairs which or even that will take you to the first floor. So it depends which context you are saying this sentence to. In a formal context, then use which. In formal, then use that. If you want to give a reason, we use why. The reason why, the reason why he called you is because he missed you. The reason why he called you is because he missed you. So here we have why that gives the reason, right, of the call in this case. So what about non-defining relative clauses? Well, they give extra information about something. And if you remove that clause, then the sentence will still make sense. Just like my example. My apartment, comma, which cost me a lot, comma, will be sold soon. Now let's take out the clause. My apartment will be sold soon. Still makes sense, right? Yes. The commas are extremely important here. So remember, my apartment, comma, relative clause, which cost me a lot, comma, will be sold soon. Let's take a look at other examples. The house, comma, whose family lives in, comma, is very shabby. So let's take out whose family lives in. The house is very shabby. It still makes sense, right? Yes. Another example. The country, comma, where I live in, comma, makes a lot of money on tourism. Let's take out the clause. The country makes a lot of money on tourism. Still makes sense. And another one, the summer, comma, when he visited me, comma, was the hottest of the decade. So if we take out the clause, the summer was the hottest of the decade. Still makes sense. Well, I have something for you. I have an example here that you need to fill in below this video. Rome is the city, and then space. We need a relative clause here. The Colosseum can be visited. I want you to answer under my video and tell me if it's non-defining or defining relative clause. So I hope you enjoyed the lesson. If you have any comments, any requests, you can comment or you can type it under this video. If you haven't subscribed to my channel, please do so. If you wish to share the lesson, please do so. Thank you very much for watching and see you next week with a new lesson. Take care, bye-bye.