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: Bile reduces the acidity of food entering from the highly acidic stomach.
Example Output: acid reduction.

Example Input: Fact: plucking a string can cause that string to vibrate.
Example Output: guitars strings sound.

Example Input: Fact: stalactites are formed by deposition.
Example Output:
deposition sand limestone.