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: vincenzo bellini (catania, november 3 1801 - puteaux, near paris, september 23 1835) was an italian composer and opera composer.
Example Output: vincenzo bellini

Example Input: aerospace engineering is a field of engineering that specializes in vehicles that move in fluids.
Example Output: aerospace engineering

Example Input: radio-frequency identification (rfid) is a technology to record the presence of an object using radio signals.
Example Output:
rfid