Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Example Input: Sentence1: weathering means breaking down rocks from larger whole into smaller pieces by weather. 
Sentence2: Trash collectors work in all types of weather, including rain and snow.
Example Output: weather

Example Input: Sentence1: Mitosis is cell division. 
Sentence2: Chromosomes are the form of the genetic material of a cell during mitosis.
Example Output: Mitosis

Example Input: Sentence1: Furthermore, antibody levels decrease with time. 
Sentence2: Passive immunity diminishes with time.
Example Output:
decrease