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.

[EX Q]: hexameter is a metrical line of verse.
[EX A]: hexameter

[EX Q]: an aloha shirt (also known as a hawaiian shirt) is a type of shirt that comes from hawaii.
[EX A]: aloha shirt

[EX Q]: the boeing e-3 sentry is a military aircraft.
[EX A]:
boeing e-3 sentry