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: mountains are formed by earthquakes. 
Sentence2: Mountains are formed by moving plates.
Example Output: are

Example Input: Sentence1: Some birds are pollinators that co-evolved with plants. 
Sentence2: insects pollinate plants.
Example Output: plants

Example Input: Sentence1: Leukemias are cancers of the blood. 
Sentence2: some viruses can cause leukemia.
Example Output:
Leukemias