This/that/these/those

Here's a detailed grammar explanation about the demonstratives "this," "that," "these," and "those":

Demonstratives are words used to point out or indicate specific people, objects, or ideas in relation to the speaker. The four main demonstratives in English are "this," "that," "these," and "those." They help us distinguish between things that are close or near ("this" and "these") and things that are far or distant ("that" and "those"). Let's examine each demonstrative individually:

1. THIS

"This" is used to refer to a singular noun or an object that is close or near in space or time to the speaker. It indicates something that is within the immediate proximity of the speaker. 

For example:

   - "This book is mine." (Referring to a book that is close to the speaker.)

   - "This is my car." (Referring to a car that the speaker is standing next to.)

2. THAT

"That" is used to refer to a singular noun or an object that is farther away in space or time from the speaker. It indicates something that is not within the immediate proximity of the speaker. 

For example:

   - "That house is beautiful." (Referring to a house that is some distance away from the speaker.)

   - "That was a great movie." (Referring to a movie that the speaker watched earlier.)

3. THESE

"These" is the plural form of "this" and is used to refer to multiple objects or people that are close or near in space or time to the speaker. It indicates things that are within the immediate proximity of the speaker. 

For example:

   - "These books are heavy." (Referring to multiple books that are close to the speaker.)

   - "These are my friends." (Referring to friends who are present with the speaker.)

4. THOSE 

"Those" is the plural form of "that" and is used to refer to multiple objects or people that are farther away in space or time from the speaker. It indicates things that are not within the immediate proximity of the speaker. 

For example:

   - "Those flowers are beautiful." (Referring to multiple flowers that are some distance away from the speaker.)

   - "Those were delicious cupcakes." (Referring to cupcakes that the speaker had earlier.)

It's important to note that the choice of using "this," "that," "these," or "those" depends on the proximity of the object or person being referred to in relation to the speaker. The context and the physical distance play a significant role in selecting the appropriate demonstrative.

Additionally, demonstratives can also be used as pronouns, replacing a noun phrase. For example:

- "I like this one." (Referring to a specific item among a group)

- "That is not what I expected." (Referring to something that doesn't meet the speaker's expectations)

In summary, "this" and "these" are used to refer to things close to the speaker, while "that" and "those" are used to refer to things farther away. The choice of demonstrative depends on the number and proximity of the objects or people being referred to.