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: Female mammals have mammary glands.
Example Output: female mammals.

Example Input: Fact: Sperm are released into the surrounding water through the osculum.
Example Output: Male gamete are sperm.

Example Input: Fact: Cells vary in size as well as shape, but all cells are very small.
Example Output:
Cells are functional unit.