In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.

Example Input: Fact: hydropower requires damming a river.
Example Output: damming river.

Example Input: Fact: sound can be used for communication by animals.
Example Output: Sound is frequency.

Example Input: Fact: tectonic plates being pushed together causes earthquakes.
Example Output:
earthquake damage.