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: a wildfire changes an ecosystem drastically. 
Sentence2: Forest fires change an ecosystem drastically.
Example Output: changes

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

Example Input: Sentence1: Evolution is a change in the characteristics of living things over time. 
Sentence2: the process of adaptation is a change in the characteristics of living things over time.
Example Output:
change