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: if an object is made of a material then that object has the properties of that material. 
Sentence2: items properties are the same as the materials the item is made of.
Example Output: made

Example Input: Sentence1: Coral reefs are made up of the accumulated exoskeletons of the coral polyp. 
Sentence2: coral polyps form reefs.
Example Output: polyp

Example Input: Sentence1: Algae and many other aquatic plants are eaten by a variety of invertebrates and fish. 
Sentence2: Certain aquatic organisms eaten by fish have varied life cycles.
Example Output:
aquatic