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: Allergens can trigger asthma attacks.

SOLUTION: allergen

PROBLEM: Sentence1: plant reproduction requires pollination. 
Sentence2: Plant reproduction requires insects and hummingbirds.

SOLUTION: plant

PROBLEM: Sentence1: a telephone is used for communication by humans over long distances. 
Sentence2: nokia is used for communication by humans over long distances.

SOLUTION:
communication