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: Fission is a type of reproduction, but a baby is the result of sexual reproduction. 
Sentence2: the fallopian tubes are used to make babies.
Example Output: baby

Example Input: Sentence1: Skin color is another polygenic trait. 
Sentence2: Skin color is influenced by multiple genes.
Example Output: Skin

Example Input: Sentence1: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement in the crust is responsible for earthquakes.
Example Output:
faulting