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: pathogens can cause disease. 
Sentence2: pathogens affects the immune system.
[A]: pathogens


[Q]: Sentence1: an animal usually requires a warm body temperature for survival. 
Sentence2: Warm blooded animals have a constant body temperature.
[A]: animal


[Q]: Sentence1: vinegar can cause harm to the eyes. 
Sentence2: Eyes: The eyes and their surrounding area are the most fragile part of the face.
[A]:
eyes