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.

Ex Input:
Sentence1: Diurnal cycles Diurnal cycles are the daily cycles of light and darkness. 
Sentence2: Plants detect and respond to diurnal cycles.

Ex Output:
Diurnal


Ex Input:
Sentence1: Contact with infected blood, contaminated needles. 
Sentence2: scraping oneself on an infected needle may cause infection.

Ex Output:
infected


Ex Input:
Sentence1: when a hemisphere is tilted away from the sun , that hemisphere receives less direct sunlight. 
Sentence2: The sun is a G star and Vega is an A star.

Ex Output:

sun