TASK DEFINITION: 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.
PROBLEM: Sentence1: Oxygen fatigue is a shortage of oxygen reaching the brain. 
Sentence2: Plants can reduce fatigue during the daytime.

SOLUTION: fatigue

PROBLEM: Sentence1: Lions live in social groups called prides. 
Sentence2: Chimpanzees live in social groups called communities.

SOLUTION: groups

PROBLEM: Sentence1: Inside the pancreas are clusters of cells called islets of Langerhans. 
Sentence2: Negative feedback controls insulin secretion by the organ that has the islets of Langerhans.

SOLUTION:
Langerhans