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 fossils of an animal or plant are found in a place then that animal or plant used to live in that place. 
Sentence2: Fossils are preserved original remains or preserved evidence of plants and animals.
Example Output: fossils

Example Input: Sentence1: Spikes are forceful the tidal waves of electric current. 
Sentence2: spikes come from tidal energy.
Example Output: Spikes

Example Input: Sentence1: skin is used for protecting the body from harmful substances. 
Sentence2: skin protects from sunlight.
Example Output:
skin