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

Ex Output:
Combustion-related


Ex Input:
Sentence1: Microbes are also called bacteria or microorganisms. 
Sentence2: Disease-causing bacteria have a negative impact on the body.

Ex Output:
bacteria


Ex Input:
Sentence1: propulsion is used for flying by a spacecraft. 
Sentence2: Propulsion was used for flying Apollo 13.

Ex Output:

flying