What part of speech is the word this?

The word "this" can be several parts of speech, depending on its function in a sentence:

* Demonstrative Adjective: When it modifies a noun, such as "this book" or "this time."

* Demonstrative Pronoun: When it stands alone as a subject or object, like "This is my favorite color" or "I like this."

* Adverb: When it modifies a verb or adjective, like "This is how you do it" or "I'm this close to finishing."

It's important to consider the context of the sentence to determine the correct part of speech.