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: Angiosperm sporophyte is dominant. 
Sentence2: Flowers form on angiosperms.
Example Output: Angiosperm

Example Input: Sentence1: an animal usually requires a warm body temperature for survival. 
Sentence2: Warm blooded animals have a constant body temperature.
Example Output: animal

Example Input: Sentence1: Enzymes help to break down proteins so that the bacteria can do their thing better. 
Sentence2: cells secrete acids to break down proteins.
Example Output:
break