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: in organic chemistry, an epoxide is a molecule that has a ring with at least three atoms in total, two carbon atoms and one oxygen atom.

A: epoxide
****
Q: the sahel is a narrow belt of land in west africa.

A: sahel
****
Q: the world wide fund for nature (wwf) is an international environmental organization.

A:
world wide fund for nature
****