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: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.
[A]: bacteria


[Q]: Sentence1: friction causes an object to lose energy. 
Sentence2: Friction occurs when surfaces rub together.
[A]: friction


[Q]: Sentence1: lack of moisture in the air causes low amounts of rainfall. 
Sentence2: Lack of humidity in the air causes low amounts of rainfall.
[A]:
air