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.

Q: Sentence1: ultraviolet light causes sunburn. 
Sentence2: Sunburn risk is higher at elevation.

A: sunburn
****
Q: Sentence1: Autumn brings the changing of the seasons. 
Sentence2: Earth 's tilt on its rotating axis causes autumn.

A: Autumn
****
Q: Sentence1: Oxygen fatigue is a shortage of oxygen reaching the brain. 
Sentence2: Plants can reduce fatigue during the daytime.

A:
fatigue
****