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: If there is no movement friction is zero. 
Sentence2: Movement causes the temperature of an object to increase.

Ex Output:
movement


Ex Input:
Sentence1: wind is used for producing electricity. 
Sentence2: Wind is caused because of pressure differences in the atmosphere.

Ex Output:
wind


Ex Input:
Sentence1: Sperm had to swim from male to female reproductive organs for fertilization. 
Sentence2: And the word for woman means a female of any age.

Ex Output:

female