Explain the usage of demonstrative determiners.

Demonstrative determiners are used to point out or indicate specific people, objects, or places. They provide information about the proximity of the noun they modify in relation to the speaker or the listener. There are four demonstrative determiners in English: "this," "that," "these," and "those."

1. "This" is used to refer to a singular noun that is close to the speaker. It indicates something that is nearby in space or time. For example:
- This book is really interesting.
- This car belongs to my friend.

2. "That" is used to refer to a singular noun that is farther away from the speaker. It indicates something that is more distant in space or time. For example:
- That house is beautiful.
- That movie was amazing.

3. "These" is used to refer to plural nouns that are close to the speaker. It indicates multiple things that are nearby in space or time. For example:
- These shoes are too tight.
- These flowers smell wonderful.

4. "Those" is used to refer to plural nouns that are farther away from the speaker. It indicates multiple things that are more distant in space or time. For example:
- Those birds are flying high in the sky.
- Those books on the shelf are mine.

Demonstrative determiners can also be used to introduce or identify something or someone. In such cases, they are followed by a noun. For example:
- This is my sister.
- That is a great idea.
- These are my favorite songs.
- Those are the keys to the car.

It is important to note that the usage of demonstrative determiners depends on the context and the speaker's perspective. The proximity can be physical, temporal, or even metaphorical. Therefore, it is crucial to consider the context and the intended meaning when using demonstrative determiners.