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: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.
Example Output: moss

Example Input: Sentence1: the mass of a planet causes the pull of gravity on that planet. 
Sentence2: the mass of a planet is what causes things to have weight.
Example Output: mass

Example Input: Sentence1: the Earth being tilted on its axis causes ones side of the Earth to receive less energy from the Sun than the other side. 
Sentence2: Energy produced by the sun in the form of heat and light is called solar energy.
Example Output:
Sun