区别就是两者意思上大致是一样的，但therefore但为副词，而so that是连词。
so that中文意思是conj,以便；所以
therefore中文意思是adv. 因此，所以
Environmental systems tend to be nonlinear, and therefore not easy to predict.环境系统一般是非线性的，所以很难预测。
He angled his chair so that he could sit and watch her.他斜移了椅子，以便坐着观察她。
