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: microscope is used to see small things by biologists by making them appear bigger. 
Sentence2: Something invented by Leeuwenhoek is used to see small things by biologists by making them appear bigger.

Ex Output:
appear


Ex Input:
Sentence1: Mitosis is cell division. 
Sentence2: mitosis often causes growth.

Ex Output:
Mitosis


Ex Input:
Sentence1: unequal heating of Earth 's surface by the Sun causes global wind patterns. 
Sentence2: Unequal absorption of radiation on the earth's surface causes global wind patterns.

Ex Output:

causes