What part of speech is the word so?

The word "so" can be a few different parts of speech depending on its use in a sentence. Here are the most common ones:

* Adverb: This is the most common use of "so." It modifies a verb, adjective, or another adverb, indicating intensity, degree, or manner.

* Example: "The music was so loud." (modifying the adjective "loud")

* Conjunction: It can introduce a subordinate clause and show a result or consequence.

* Example: "He was so tired that he fell asleep on the couch." (introducing the subordinate clause "that he fell asleep on the couch")

* Pronoun: It can act as a substitute for a previously mentioned noun or noun phrase.

* Example: "I am feeling tired, so I'm going to bed." (referring to the previous statement about being tired)

Let me know if you'd like more examples or want to explore other less common uses of "so"!