"Drama" refers to the art of the stage play. "Dramatic" means something big and attention-getting, like an actor using big actions so everyone can see him. My high school science teacher was explaining how a pump works and why you need to prime it by pouring water into it. As he said "by pouring water into it," he poured a little water onto the floor. This illustrated his words in a dramatic way, acting them out as he said them. That was dramatic, but it wasn't drastic because a little water doesn't hurt a floor. "Drastic" means something extreme or excessive. "The student would not stop playing games on his smartphone. The teacher took drastic action. He threw the phone out the window." That would be both drastic and dramatic.