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: First, the bottle is calibrated with a graduated cylinder. 
Sentence2: calibration is performed with a cylinder.
Example Output: calibrated

Example Input: Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: Another common snail is the decollate snail.
Example Output: snail

Example Input: Sentence1: camouflage is used for protection by prey against predators. 
Sentence2: Many animals camouflage or protect themselves by blending into their surroundings.
Example Output:
camouflage