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: protein is used to repair cells by the human body. 
Sentence2: Meat, fish and chicken are rich sources of protein.
[A]: protein


[Q]: Sentence1: electric devices require electrical energy to function. 
Sentence2: Lie detectors are electrical or mechanical devices.
[A]: devices


[Q]: Sentence1: friction causes the speed of an object to decrease. 
Sentence2: The texture of surfaces can cause the speed of an object to decrease.
[A]:
decrease