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: dropping an object into water causes vibrations in the water. 
Sentence2: Dropping an object into lake causes vibrations.
Example Output: dropping

Example Input: Sentence1: exercise increases a body 's strength. 
Sentence2: Exercise is more than running and lifting.
Example Output: exercise

Example Input: Sentence1: Most organisms consume--and are consumed by--more than one species. 
Sentence2: most living things consume and are consumed by more than one species.
Example Output:
Most