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.

Example Input: mae west (august 17, 1893 – november 22, 1980) was an american actress and movie star.
Example Output: mae west

Example Input: zinc phosphate is a chemical compound.
Example Output: zinc phosphate

Example Input: a marriage proposal is when one person in a relationship asks the other person to marry them.
Example Output:
marriage proposal