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: diana ross is a famous american soul and pop singer.

SOLUTION: diana ross

PROBLEM: kappa (uppercase/lowercase Κ κ), is the letter of the greek alphabet, used to represent the "k" sound in ancient and modern greek.

SOLUTION: kappa

PROBLEM: archerfish (or archer fish) are small fish.

SOLUTION:
archerfish