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

Example Input: Sentence1: Combustion generates toxic fumes. 
Sentence2: High temperatures can cause toxic fumes.
Example Output: fumes

Example Input: Sentence1: Fish are animals that live in water and breathe using gills. 
Sentence2: Fish use their gills to breathe water.
Example Output:
Fish