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: the uterus is used in reproduction. 
Sentence2: Reproduction uses the same organ as menstruation.
Example Output: reproduction

Example Input: Sentence1: Mangoes are propagated vegetatively and by seeds. 
Sentence2: animals propagate mangoes.
Example Output: Mangoes

Example Input: Sentence1: Macaques are known for their aggressive behavior. 
Sentence2: macaques intend to cause harm or pain.
Example Output:
Macaques