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: Boiling water can cause burns. 
Sentence2: heating water can cause burns.

Ex Output:
water


Ex Input:
Sentence1: Combustion-related, motor vehicles, wood burning, open burning, industrial processes. 
Sentence2: Combustion is used to produce heat.

Ex Output:
Combustion-related


Ex Input:
Sentence1: Mutations are essential for evolution to occur. 
Sentence2: Changes in DNA sequences are essential for evolution to occur.

Ex Output:

essential