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.

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

A: diana ross
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Q: the cyclostomes (or cyclostomata) are the lamprey and hagfish.

A: cyclostome
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Q: skin effect is the tendency of an alternating electric current to flow towards the perimeter of a conductor and leave the center part of the conductor without (or barely) any electricity flow.

A:
skin effect
****