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: Mammals depend on the vegetation for food and shelter. 
Sentence2: Mammals are Heterotrophs.
Example Output: Mammals

Example Input: Sentence1: Without light there is no sense of vision. 
Sentence2: Glass causes a sense of vision.
Example Output: sense

Example Input: Sentence1: a freezer is used for cooling things. 
Sentence2: Heat removal in convection cooling is based on the physical properties of the cooling media.
Example Output:
cooling