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: a switch is used to start the flow of current in an electrical circuit. 
Sentence2: lights are on when there is flow of current in an electrical circuit.
Example Output: circuit

Example Input: Sentence1: when a hemisphere is tilted away from the sun , that hemisphere receives less direct sunlight. 
Sentence2: Sunlight is delivered in small packets of energy called photons.
Example Output: sunlight

Example Input: Sentence1: sexual reproduction increases genetic diversity. 
Sentence2: Genetic diversity is a result of genetic material exchanged during reproduction.
Example Output:
diversity