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: An example of a cartilaginous fish is a shark. 
Sentence2: jaws make sharks excellent predators.
Example Output: shark

Example Input: Sentence1: Water is essential for all life on Earth. 
Sentence2: H2O is needed for all life on Eartth.
Example Output: Earth

Example Input: Sentence1: the gravitational pull of the Moon on Earth 's oceans causes the tides. 
Sentence2: the gravitational pull of the Moon on Earth 's oceans causes water to rise and fall.
Example Output:
Earth