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: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: Yeast and mushrooms are types of fungus.
Example Output: mushrooms

Example Input: Sentence1: Flatworms Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. 
Sentence2: Tapeworms belong to the phylum Platyhelminthes.
Example Output: tapeworms

Example Input: Sentence1: Metazoan phylogeny Phylogeny of phyla is poorly understood. 
Sentence2: The evolutionary history of metazoas is poorly understood.
Example Output:
Metazoan

