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: a sawfly is an insect belonging to suborder symphyta of the order hymenoptera.
Example Output: sawfly

Example Input: a diode is an electronic component with two electrodes (connectors) that allows electricity to go through it in one direction and not the other direction.
Example Output: diode

Example Input: world heritage sites are places in the world which are very important from the cultural or natural point of view.
Example Output:
world heritage site