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

Ex Output:
reproduction


Ex Input:
Sentence1: Most people know that the Venus Flytrap is a carnivorous plant. 
Sentence2: The Venus Flytrap has specialized reproductive organs.

Ex Output:
Flytrap


Ex Input:
Sentence1: Mollusks have a circulatory system with one or two hearts that pump blood. 
Sentence2: Arthropods and most mollusks have an open circulatory system.

Ex Output:

Mollusks