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: Climate refers to weather over a long period of time. 
Sentence2: weather is generally described in terms of temperature and moisture.
Example Output: long

Example Input: Sentence1: if humans disturb animals in a location then those animals will move to a different location. 
Sentence2: The human being is self-aware.
Example Output: humans

Example Input: Sentence1: cutting down trees has a negative impact on an ecosystem. 
Sentence2: Deforestation takes place when trees are cut down in the rainforest.
Example Output:
cutting