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.

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

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

Example Input: Sentence1: a vehicle is used for transportation. 
Sentence2: most bigger cities require vehicles.
Example Output:
vehicle