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.

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

Ex Output:
sense


Ex Input:
Sentence1: Weather today is said to be sunny and clear. 
Sentence2: High pressure systems cause it to be sunny.

Ex Output:
sunny


Ex Input:
Sentence1: Ethologists usually study how animals behave in their natural environment. 
Sentence2: Ethology is the study of behavior.

Ex Output:

behave