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: cold fronts cause thunderstorms as they pass by. 
Sentence2: Thunderstorms create havoc.
Example Output: thunderstorms

Example Input: Sentence1: evaporation can be used for separating a solute from a solvent in a solution. 
Sentence2: Evaporation can be used for segregation a solute from a solvent in a solution.
Example Output: a

Example Input: Sentence1: If climate changes and temperatures rise, there are a number of potential effects. 
Sentence2: Climate change is a phase change.
Example Output:
changes