so is one of the most commonly used words in English with multiple meanings:
1. As an adverb meaning "to such a great extent" - "I'm so tired!"
2. As a conjunction meaning "therefore" - "It was raining, so we stayed home."
3. In informal speech as a filler word - "So, what do you think?"
4. To express agreement - "That's so true!"
5. In "so that" constructions indicating purpose - "I studied hard so that I could pass the exam."