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: Fractures heal when osteoclasts form new bone. 
Sentence2: Fractures A fracture is a broken or cracked bone.

Ex Output:
Fractures


Ex Input:
Sentence1: Earth's Atmosphere Earth's atmosphere is the layer of gasses that surrounds the earth. 
Sentence2: weather refers to the conditions in the layer of gasses that surrounds the earth.

Ex Output:
earth


Ex Input:
Sentence1: Rocket propellants are the fuels and the oxidizers carried by the rocket for propulsion. 
Sentence2: oxidizers are used for flying a spacecraft.

Ex Output:

oxidizers