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: Heat and temperature are the same. 
Sentence2: a thermometer is used to measure heat.

Ex Output:
Heat


Ex Input:
Sentence1: Most copepods feed on phytoplankton. 
Sentence2: most copepods feed on bacteria and algae that use sunlight to make food.

Ex Output:
copepods


Ex Input:
Sentence1: Tunicates reproduce sexually. 
Sentence2: Tunicates are sea creatures encased by tough membranes, reminiscent of tunics.

Ex Output:

Tunicates