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.
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Question: spintronics is a kind of electronics that uses the tiny magnetic fields that come from electrons as well as their electric charge.

Answer: spintronics


Question: a mathematician's apology is a book about mathematics which was written in 1940.

Answer: a mathematician's apology


Question: the greenland sea is a body of water.

Answer:
greenland sea