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.

Input: Consider Input: Sentence1: camouflage is used for protection by prey against predators. 
Sentence2: blending is used for protection.

Output: protection


Input: Consider Input: Sentence1: Sound vibrations can be compared to pond ripples. 
Sentence2: dropping an object into water causes pond ripples.

Output: pond


Input: Consider Input: Sentence1: Social behavior is organized by social relationships. 
Sentence2: Insects may live in large colonies and have complex social relationships.


Output: relationships