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: Ribosomes are structures in the cytoplasm where proteins are made. 
Sentence2: prokaryotes can make proteins.
Example Output: made

Example Input: Sentence1: Some herbivores have more than one stomach. 
Sentence2: Camels are an herbivore.
Example Output: herbivores

Example Input: Sentence1: optical tools are used for observing materials up close. 
Sentence2: A microscope is an optical tool.
Example Output:
optical