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: Lymph is a fluid that leaks out of capillaries into spaces between cells. 
Sentence2: Humans are made up of trillions of cells.

Ex Output:
cells


Ex Input:
Sentence1: Growth usually ceases with puberty. 
Sentence2: Growth usually ceases when humans become sexually mature.

Ex Output:

Growth