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: Heat and temperature are the same. 
Sentence2: a thermometer is used to measure heat.
Example Output: Heat

Example Input: Sentence1: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.
Example Output: bacteria

Example Input: Sentence1: Runoff water is wasted water. 
Sentence2: Streams may start with wasted water.
Example Output:
wasted