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: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: Yeast and mushrooms are types of fungus.

SOLUTION: mushrooms

PROBLEM: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: Antigens are proteins foreign to the body.

SOLUTION: antigen

PROBLEM: Sentence1: Astroglial cells are the most common cells in brain tissue. 
Sentence2: astroglial cells die if their oxygen supply is cut off.

SOLUTION:
Astroglial