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: Most soil nutrients are cations. 
Sentence2: decomposition increases the amount of cations in the soil.
Example Output: cations

Example Input: Sentence1: Lions live in social groups called prides. 
Sentence2: Chimpanzees live in social groups called communities.
Example Output: groups

Example Input: Sentence1: wind and rain cause erosion. 
Sentence2: water causes erosion most effectively.
Example Output:
erosion