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: Landslides Seismic vibration is a common triggering mechanism for landslides. 
Sentence2: Erosion can cause seismic vibrations which are triggering mechanisms.

Output: Seismic


Input: Consider Input: Sentence1: a rainbow is formed by refraction of light by separating light into all different colors. 
Sentence2: Rainbows form when raindrops refract sunlight.

Output: refraction


Input: Consider Input: Sentence1: Bacteria can cause infection. 
Sentence2: Bacteria can cause bodily tissues to swell.


Output: Bacteria