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.

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

Output: tapeworms

Input: Consider Input: Sentence1: Oxygen fatigue is a shortage of oxygen reaching the brain.
Sentence2: Plants can reduce fatigue during the daytime.

Output: fatigue

Input: Consider Input: Sentence1: Plasma is more common in stars, because making plasma requires high temperatures.
Sentence2: Plasma is formed in high temperatures of the sun.
Output: high