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.
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Question: Sentence1: friction causes an object to lose energy. 
Sentence2: Friction occurs when surfaces rub together.

Answer: friction


Question: Sentence1: If there is sun, there is sunlight, there is day. 
Sentence2: Energy enters ecosystems from the sun.

Answer: sun


Question: Sentence1: Blood type is important for medical reasons. 
Sentence2: Type O blood types are defined generally as warriors.

Answer:
Blood