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.

Example Input: Sentence1: cell division often causes growth. 
Sentence2: Mitosis is cell division.
Example Output: cell

Example Input: Sentence1: Insect wings are attached to the dorsal side of their thorax. 
Sentence2: wings are attached to the dorsal side of the insect.
Example Output: dorsal

Example Input: Sentence1: when the seasons change from the summer to the fall , the amount of daylight will decrease. 
Sentence2: Then the days become colder and the number of daylight hours decreases.
Example Output:
daylight