Therefore
denotes that X is so, therefore Y happened. coming from explanatory の・んだ and Causation. Unlike から, it does not imply causation, only correlation. (ので vs から)
ちょっと忙しいので、そろそろ失礼します。 I'm a little busy, therefore I'll be making my leave soon.
ここは静かなので、とても煩ないです。 Because it's very quiet here, it's very not-annoying.