Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.

diana ross is a famous american soul and pop singer.
diana ross

defibrillation is the act of defibrillating the heart to treat the heart when it is not pushing blood because the heart muscle is not working in any pattern.
defibrillation

dark rainbow is an indian bollywood movie, directed by abhik bhanu.

dark rainbow