so is one of the most commonly used words in English with multiple meanings:
1. As an adverb: "I'm so tired today." (very)
2. As a conjunction: "It was raining, so we stayed home." (therefore)
3. In internet slang: "That's so last year!" (totally)
4. As a filler word: "So, what do you think?" (well)
5. In song lyrics: "I love you so..." (very much)