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: Flowers produce seeds for reproduction. 
Sentence2: flowers require dispersal for reproduction.
Example Output: Flowers

Example Input: Sentence1: People of all ages and activity levels perspire or sweat. 
Sentence2: Perspiration reduces body heat.
Example Output: perspire

Example Input: Sentence1: friction causes the temperature of an object to increase. 
Sentence2: pressure causes the temperature of an object to increase.
Example Output:
causes