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 solution is formed by one substance being dissolved in another substance. 
Sentence2: A solution is formed when limestone is dissolved in ocean water.
Example Output: formed

Example Input: Sentence1: Heterotrophs are living things that cannot make their own food. 
Sentence2: food contains organic molecules.
Example Output: food

Example Input: Sentence1: Earth 's tilt on its rotating axis causes seasons to change. 
Sentence2: Earth 's tilt on its rotating axis causes autumn.
Example Output:
Earth