"So" is a versatile word in the English language, primarily used as a conjunction or adverb. As a conjunction, it connects clauses, indicating a result or consequence, such as in the sentence, "It was raining, so we stayed indoors." As an adverb, it can emphasize a degree or extent, as in "I am so tired." In addition to its grammatical uses, "so" can also function as a filler word in conversation, often used to transition between thoughts. For example, someone might say, "So, what do you think?" This informal usage helps to maintain the flow of dialogue and engage listeners.