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: wind is used for producing electricity. 
Sentence2: Winds are caused by pressure differences.

SOLUTION: wind

PROBLEM: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: Allergens can trigger asthma attacks.

SOLUTION: allergen

PROBLEM: Sentence1: Because of the big wave action, the rocks are very smooth. 
Sentence2: Wave action can cause rocks to contact over time.

SOLUTION:
action