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: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Bamboos are vigorous, rugged plants.

SOLUTION: Plants

PROBLEM: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: molds are antigens.

SOLUTION: antigen

PROBLEM: Sentence1: when the season changes , the amount of daylight will change. 
Sentence2: Seasons occur due to the tilt of the Earth's axis and the orbit of the Earth around the Sun.

SOLUTION:
season