deshalb, trotzdem, sonst, außerdem

These adverbs connect two main clauses. When one of them starts the second sentence, it takes position 1, so the conjugated verb comes next and the subject follows: Es regnet. Deshalb nehme ich einen Schirm mit. (It's raining. That's why I'm taking an umbrella.)

• deshalb, darum, deswegen, daher: that's why, therefore (a result)
• trotzdem: anyway, nevertheless (the opposite of what you expect)
• sonst: otherwise (the bad result if you don't do it)
• außerdem: besides, in addition (one more point)
• danach, dann: after that, then (the next step)

sonst usually follows a comma after a request: Beeil dich, sonst verpassen wir den Bus! Unlike weil or obwohl, these words never send the verb to the end.