So (a coordinating conjunction) “So” is more informal and is commonly used in spoken English. *It was raining, so I took an umbrella. Therefore (a conjunctive adverb) “Therefore” is more formal and is often used in written English, especially in academic or logical arguments. *He was the most knowledgeable person. Therefore, he seemed like the best candidate. #ieltsgrammar #ieltsspeaking #ieltswriting