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.

Ex Input:
Sentence1: Finally, the fluid in the nephron reaches a collecting duct . 
Sentence2: fluid in the kidneys collect into ducts.

Ex Output:
fluid


Ex Input:
Sentence1: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: All chordates are vertebrates.

Ex Output:
Chordates


Ex Input:
Sentence1: disease-causing microbes have a negative impact on the body. 
Sentence2: Dangerous microbes are called pathogenic or disease causing.

Ex Output:

microbes