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: Chemical weathering is the chemical disintigration of rocks. 
Sentence2: moss causes the chemical disintigration of rocks.

Ex Output:
chemical


Ex Input:
Sentence1: condensing causes a liquid to form. 
Sentence2: Air carries moisture that causes a liquid to form.

Ex Output:
causes


Ex Input:
Sentence1: chemical splashing can cause harm to humans. 
Sentence2: Ozone is harmful to humans and crops.

Ex Output:

humans