TASK DEFINITION: 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.
PROBLEM: the river trent is one of the major rivers of england.

SOLUTION: river trent

PROBLEM: a hospital ship is a big boat which is built to cure patients.

SOLUTION: hospital ship

PROBLEM: bunsei (文政) was a japanese era name (年号, "nengō", lit.

SOLUTION:
bunsei