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

SOLUTION: antigen

PROBLEM: Sentence1: Nitrogen is found in proteins, nucleic acids, and chlorophyll. 
Sentence2: Lawns eat nitrogen.

SOLUTION: Nitrogen

PROBLEM: Sentence1: water vapor condensing in clouds causes rain. 
Sentence2: Condensing is a gas turning into a liquid.

SOLUTION:
condensing