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: cold fronts cause thunderstorms as they pass by. 
Sentence2: Thunderstorms create havoc.

A: thunderstorms
****
Q: Sentence1: Proper digestion is vital for nutrient absorption. 
Sentence2: Digestion is important for an animal's survival.

A: digestion
****
Q: Sentence1: Salinity is vital for animals that live in the ocean. 
Sentence2: Coral reefs provide food and shelter to animals that require salinity.

A:
Salinity
****