"This" is a demonstrative pronoun, and it usually functions as the subject or object of a sentence. To end a sentence grammatically, you need a complete thought, and "this" alone doesn't provide that.
Here's why:
* Incomplete thought: "This" refers to something, but it doesn't tell us anything about that thing.
* Missing verb: Sentences need a verb to express an action or state of being.
Example:
* Incorrect: "I like this."
* Correct: "I like this book."
Let me know if you'd like to try another sentence! 😊