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.
--------
Question: 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.

Answer: epoxide


Question: adam lambert (born january 29, 1982 in indianapolis, indiana) is an american pop rock singer-songwriter.

Answer: adam lambert


Question: separate but equal was a legal doctrine that existed in the united states for 58 years.

Answer:
separate but equal